The exchange-coupled [Co/Ni]N/Tb Fe nano-magnetic films can display strong perpendicular magnetic anisotropy(PMA) which depends on the Tb:Fe component ratio, Tb Fe layer thickness and the repetition number N of [Co/Ni...The exchange-coupled [Co/Ni]N/Tb Fe nano-magnetic films can display strong perpendicular magnetic anisotropy(PMA) which depends on the Tb:Fe component ratio, Tb Fe layer thickness and the repetition number N of [Co/Ni]Nmultilayer. Perpendicular spin valves in the nano thickness scale, consisting of a [Co/Ni]3free and a [Co/Ni]5/Tb Fe reference multilayer, show high giant magnetoresistance(GMR) signal of 6.5 % and a large switching field difference over3 k Oe. However, unexpected slanting of the free layer magnetization, accompanied by a reduced GMR ratio, was found to be caused by the presence of a thick Fe-rich or even a thin but Tb-rich Tb Fe layer. We attribute this phenomenon to the large magnetostriction effect of Tb Fe which probably induces strong stress acting on the free layer and hence reduces its interfacial PMA.展开更多
The extra heat generation in spin transport is usually interpreted in terms of the spin relaxation. Reformulating the heat generation rate, we find alternative current-force pairs without cross effects, which enable u...The extra heat generation in spin transport is usually interpreted in terms of the spin relaxation. Reformulating the heat generation rate, we find alternative current-force pairs without cross effects, which enable us to interpret the product of each pair as a distinct mechanism of heat generation. The results show that the spin-dependent part of the heat generation includes two terms. One is proportional to the square of the spin accumulation and arises from the spin relaxation. However, the other is proportional to the square of the spin-accumulation gradient and should be attributed to another mechanism, the spin diffusion. We illustrate the characteristics of the two mechanisms in a typical spin valve with a finite nonmagnetic spacer layer.展开更多
We propose two possible spin valves based on a zigzag silicene nanoribbon（ZSR） ferromagnetic junction. By using the Landauer–B u¨tikker formula, we calculate the spin-resolved conductance spectrum of the syste...We propose two possible spin valves based on a zigzag silicene nanoribbon（ZSR） ferromagnetic junction. By using the Landauer–B u¨tikker formula, we calculate the spin-resolved conductance spectrum of the system and find that the spin transport is crucially dependent on the band structure of the ZSR tuned by a perpendicular electric field. When the ZSR is in the topological insulator phase under a zero electric field, the low-energy spin transport and its ON and OFF states in the tunneling junction mainly rely on the valley valve effect and the edge state of the energy band, which can be electrically modulated by the Fermi level, the spin–orbit coupling, and the local magnetization. When a nonzero perpendicular electric field is applied, the ZSR is a band insulator with a finite energy gap, the spin switch phenomenon is still preserved in the device and it does not come from the valley valve effect, but from the energy gap opened by the perpendicular electric field. The proposed device might be designed as electrical tunable spin valves to manipulate the spin degree of freedom of electrons in silicene.展开更多
Top and bottom NiO-pinning spin valves of Si/Ta/NiO/Co/Cu/Co/Ta and Si/Ta/Co/Cu/Co/NiO/Ta were prepared by magnetron sputtering, and X-ray diffraction and giant magnetoresistance （GMR） ratio were measured in the tem...Top and bottom NiO-pinning spin valves of Si/Ta/NiO/Co/Cu/Co/Ta and Si/Ta/Co/Cu/Co/NiO/Ta were prepared by magnetron sputtering, and X-ray diffraction and giant magnetoresistance （GMR） ratio were measured in the temperature range from 5 to 300 K. For the bottom spin valve, the interracial roughness at NiO/Co is much smaller than that of Co/NiO in the top one. The Co/Cu and Cu/Co interfaces have the same roughness in the bottom and the top spin valves. NiO, Co, and Cu layers have （111） preferred orientations in the top one and random orientations in the bottom one. The GMR ratio of the bottom spin valve is larger than that of the top one at all temperatures and their difference increases with decreasing temperature.展开更多
Spin injection, spin diffusion, and spin detection are investigated in Co/Ag/Co lateral spin valves at room temperature.Clear spin accumulation signals are detected by the non-local measurement. By fitting the results...Spin injection, spin diffusion, and spin detection are investigated in Co/Ag/Co lateral spin valves at room temperature.Clear spin accumulation signals are detected by the non-local measurement. By fitting the results to the one-dimensional diffusion equation,8.6% spin polarization of the Co/Ag interface and -180 nm spin diffusion length in Ag are obtained.Thermal treatment results show that the spin accumulation signal drastically decreases after 100℃ annealing, and disappears under 200℃ annealing. Our results demonstrate that, compared to the spin diffusion length, the decrease and the disappearance of the spin accumulation signal are mainly dominated by the variation of the interfacial spin polarization of the Co/Ag interface.展开更多
Interface engineering in device fabrication is a significant but complicated issue.Although great successes have been achieved by conventional physical in situ or ex situ methods,it still suffers from complicated proc...Interface engineering in device fabrication is a significant but complicated issue.Although great successes have been achieved by conventional physical in situ or ex situ methods,it still suffers from complicated procedures.In this work,we present a facile method for fabricating phthalocyanine(Pc)-based two-dimensional conductive metal–organic framework(MOF)films.Based on PcM-Cu(M=Ni,Cu,H_(2))MOF films,spin valves with a vertical configuration of La_(0.67)Sr_(0.33)MnO_(3)/PcM-Cu MOFs/Co were constructed successfully,and exhibited notably high negative magnetoresistance(MR)up to -22% at 50 K.The penetrated Co atoms coordinated with the dehydrogenated hydroxy groups in the MOFs resulting in an antiferromagnetic layer of the PcM-Cu-Co hybrid structure.Interestingly,a significant exchange bias effect was demonstrated at the PcM-Cu MOF/Co interface,beneficial for the MR behavior.Thus,our present study provides new insights into developing high-performance organic spin valves via de novo molecular design.展开更多
Organic spin valve (OSV), one of the most promising and representative devices involving spin injection, transport and detection, has drawn tremendous attention owing to their ultra-long spin relaxation time in the fi...Organic spin valve (OSV), one of the most promising and representative devices involving spin injection, transport and detection, has drawn tremendous attention owing to their ultra-long spin relaxation time in the field of molecular spintronics. Since the first demonstration of truly worked vertical OSV device in 2004, efforts in enhancement of high performance and pursuit of spin-related nature have been devoted in related field. It offers a new opportunity to develop the integrated flexible multi-functional arrays based on spintronics in the future. However, the unreliable working state in OSVs due to the lack of exploration on interface control will cause severe impact on the performance evaluation and further restrict their practical application. Herein, we focus on the recent progress in strategies for reliable fabrication and evaluation of typical OSVs in vertical configuration. Firstly, the challenges in protection of two spin interface properties and identification of spin-valve-like signals were proposed. Then, three points for attention including selection of bottom electrodes, optimization of organic spacer, and prevention of metal penetration to improve the device performance and reliability were mentioned. Particularly, various modified strategies to solve the “dead layer” issue were highlighted. Furthermore, we discussed the general protocols in the reliable evaluation of OSVs’ performance and transport mechanism identification. Notably, several key fundamentals resulting in spurious magnetoresistance (MR) response were illustrated. Finally, we also highlighted the future perspectives on spintronic devices of organic materials.展开更多
Microstructure of NiO-containing Co/Cu/Co spin valves （CCC-SV） annealed at room temperature for nearly four years has been studied by synchrotron radiation X-ray diffraction. With the annealing time expanding, the t...Microstructure of NiO-containing Co/Cu/Co spin valves （CCC-SV） annealed at room temperature for nearly four years has been studied by synchrotron radiation X-ray diffraction. With the annealing time expanding, the thickness of each sub-layer remains nearly unchanged while the interface roughness varies obviously compared with that of samples without annealing. The roughness at the interface of NiO/Co decreases with the annealing time increasing for both of the samples with NiO layer on the top （TSV） and under the bottom （BSV） of CCC-SV. On the other hand, the roughness at Co/Cu interface increases with the annealing time expanding for BSV while it decreases for TSV. These results indicate that the structure of TSV is more stable than that of BSV.展开更多
Pseudo spin valves（SVs） exhibiting perpendicular magnetic anisotropy were prepared by magnetron sputtering. Magnetization measurements of the Co/Pt multilayers were performed to select the reference and free layers....Pseudo spin valves（SVs） exhibiting perpendicular magnetic anisotropy were prepared by magnetron sputtering. Magnetization measurements of the Co/Pt multilayers were performed to select the reference and free layers. The selection criteria are square magnetic hysteresis loops, weaker current shunting effect, and proper coercivity. The optimal reference layer and free layer are Pt（5.0 nm）/[Co（0.4 nm）/Pt（0.6 nm）]3/Co（0.4 nm）/Cu（3.0 nm）and Cu（3.0 nm）/[Co（0.4 nm）/Pt（1.5 nm）]4, respectively.The resulting pseudo SV exhibits two well-separated hysteresis loops when the field is applied perpendicular to the film plane. The minor hysteresis loop corresponding to the free layer shifts toward negative direction of the magnetic field axis, indicating ferromagnetic interlayer exchange coupling between the two magnetic layers. The coupling also enhances the coercivity（HC） of both layers. The perpendicular giant magnetoresistance（GMR） of 2.7 % is achieved with current in plane measurement. The GMR first increases when Pt seed layer is thickened, reaches a maximum of 3.0 % at 4 nm and then decreases with the further increase of thickness. But thicker Cu spacer layer always lowers the GMR of the SV.展开更多
Different than covalently bonded magnetic multilayer systems,high-quality interfaces without dangling bonds in van der Waals(vd W)junctions of two-dimensional(2D)layered magnetic materials offer opportunities to reali...Different than covalently bonded magnetic multilayer systems,high-quality interfaces without dangling bonds in van der Waals(vd W)junctions of two-dimensional(2D)layered magnetic materials offer opportunities to realize novel functionalities.Here,we report the fabrication of multi-state vertical spin valves without spacer layers by using vd W homo-junctions in which exfoliated Fe3GeTe2 nanoflakes act as ferromagnetic electrodes and/or interlayers.We demonstrate the typical behavior of two-state and threestate magnetoresistance for devices with two and three Fe3GeTe2 nanoflakes,respectively.Distinct from traditional spin valves with sandwich structures,our novel homo-junction-based spin-valve structure allows the straightforward realization of multi-state magnetic devices.Our work demonstrates the possibility of extend multi-state,non-volatile spin information to 2 D magnetic homo-junctions,and it emphasizes the utility of vd W interface as a fundamental building block for spintronic devices.展开更多
Single crystals of organic semiconductors with perfect crystal structure and minimal density of defects can exhibit high mobility and low spin scattering compared with their amorphous or polycrystalline counterparts.T...Single crystals of organic semiconductors with perfect crystal structure and minimal density of defects can exhibit high mobility and low spin scattering compared with their amorphous or polycrystalline counterparts.Therefore,these materials are promising candidates as the spin transport media to obtain long spin relaxation times and spin diffusion lengths in spintronic devices.However,the investigation of spin injection and transport properties in organic single crystals is hindered by the inability to construct devices such as single-crystalline organic spin valves(OSVs).Herein,thin and large organic single crystals of 6,13-bis(triisopropylsilylethynyl)pentacene(TIPS-pentacene)were grown on a liquid substrate and transferred to a target substrate carrying ferromagnetic electrodes to construct single-crystalline OSVs.The magnetoresistance(MR)responses of the single crystals were investigated to study their spin injection and transport properties.MR value as high as 17%was probed with an intermediate layer thickness of 269 nm.More importantly,spin transport was still observed in a single crystal of a thickness up to 457 nm,which was much larger than that of polycrystalline thin film.Our research provides a general methodology for constructing single-crystalline OSVs and paves the way to probe the intrinsic spin transport properties of organic semiconductors based on single crystals.展开更多
The spin transport was investigated in permally （Py）/MgO/Ag junction with lateral spin valve structure. Non-local lateral spin valves measurement was carried out to determin, the apin accumulignal in Ag strip, and t...The spin transport was investigated in permally （Py）/MgO/Ag junction with lateral spin valve structure. Non-local lateral spin valves measurement was carried out to determin, the apin accumulignal in Ag strip, and the spin dif u^sion - length in Ag of the lateral spin valves was extracted from devices with the different distances between injector and detector. The experimental results are found that spin accumulation and spin diffusion length （2s） could be significantly enhanced in Ag strip with MgO capping layer, and those effects may be attributed to the low-surface spin scattering rate in Ag with an MgO cap- ping layer.展开更多
Magnetoelectric coupling has been a trending research topic in both organic and inorganic materials and hybrids.The concept of controlling magnetism using an electric field is particularly appealing in energy efficien...Magnetoelectric coupling has been a trending research topic in both organic and inorganic materials and hybrids.The concept of controlling magnetism using an electric field is particularly appealing in energy efficient applications.In this spirit,ferroelectricity has been introduced to organic spin valves to manipulate the magneto transport,where the spin transport through the ferromagnet/organic spacer interfaces(spinterface)are under intensive study.The ferroelectric materials in the organic spin valves provide a knob to vary the interfacial energy alignment and the interfacial crystal structures,both are critical for the spin transport.In this review,we introduce the recent efforts of controlling magnetoresistance of organic spin valves using ferroelectricity,where the ferroelectric material is either inserted as an interfacial layer or used as a spacer material.The realization of the ferroelectric control of magneto transport in organic spin valve,advances our understanding in the spin transport through the ferromagnet/organic interface,and suggests more functionality of organic spintronic devices.展开更多
Flexible spin valves were prepared by magnetron sputtering on polyimide substrates. The buffer layer that reduces significantly the effect of the polymer substrate on the spin valve microstructure and magnetoresistive...Flexible spin valves were prepared by magnetron sputtering on polyimide substrates. The buffer layer that reduces significantly the effect of the polymer substrate on the spin valve microstructure and magnetoresistive properties was revealed. Bending deformation was applied to the microobjects based on the flexible spin valves in parallel to anisotropy axes. It was revealed that during the bend the magnetoresistance changes due to the joint impact of both the change of the magnetic field projection on the film plane and the change of the magnetic properties of the ferromagnetic layers. The obtained dependences have been used in construction of bending sensor, in which the flexible spin valve microstripes were united into the Wheatstone bridge.展开更多
A single-molecule magnet is a long-sought-after nanoscale component because it can enable us to miniaturize nonvolatile memory storage devices.The signature of a single-molecule magnet is switching between two bistabl...A single-molecule magnet is a long-sought-after nanoscale component because it can enable us to miniaturize nonvolatile memory storage devices.The signature of a single-molecule magnet is switching between two bistable magnetic ground states under an external magnetic field.Based on this feature,we theoretically investigate a magnetic-fieldcontrolled reversible resistance change active at low temperatures in a molecular magnetic tunnel junction,which consists of a single-molecule magnet sandwiched between a ferromagnetic electrode and a normal metal electrode.Our numerical results demonstrate that the molecular magnetism orientation can be manipulated by magnetic fields to be parallel/antiparallel to the ferromagnetic electrode magnetization.Moreover,different magnetic configurations can be“read out”based on different resistance states or different spin polarization parameters in the current spectrum,even in the absence of a magnetic field.Such an external magnetic field-controlled resistance state switching effect is similar to that in traditional spin valve devices.The difference between the two systems is that one of the ferromagnetic layers in the original device has been replaced by a magnetic molecule.This proposed scheme provides the possibility of better control of the spin freedom of electrons in molecular electrical devices,with potential applications in future high-density nonvolatile memory devices.展开更多
The magnetoresistance behavior and the magnetization reversal mode of NiFe/Cu/CoFe/IrMn spin valve giant magnetoresistance （SV-GMR） in nanoscale were investigated experimentally and theoretically by nanosized magnet...The magnetoresistance behavior and the magnetization reversal mode of NiFe/Cu/CoFe/IrMn spin valve giant magnetoresistance （SV-GMR） in nanoscale were investigated experimentally and theoretically by nanosized magnetic simulation methods. Based on the Landau-Lifshitz-Gilbert equation, a model with a special gridding was proposed to calculate the giant magnetoresistance ratio （MR） and investigate the magnetization reversal mode. The relationship between MR and the external magnetic field was obtained and analyzed. Studies into the variation of the magnetization distribution reveal that the magnetization reversal mode, that is, the jump variation mode for NiFe/Cu/CoFe/IrMn, depends greatly on the antiferromagnetic coupling behavior between the pinned layer and the antiferromagnetic layer. It is also found that the switching field is almost linear with the exchange coefficient.展开更多
A multilayered spin valve film with a structure of Ta(5 nm)/Co_(75)Fe_(25)(5 nm)/Cu(2.5 nm)/Co_(75)Fe_(25)(5 nm)/Ir_(20)Mn_(80)(12 nm)/Ta(8 nm)is prepared by the high-vacuum direct current(DC)magnetron sputtering.The ...A multilayered spin valve film with a structure of Ta(5 nm)/Co_(75)Fe_(25)(5 nm)/Cu(2.5 nm)/Co_(75)Fe_(25)(5 nm)/Ir_(20)Mn_(80)(12 nm)/Ta(8 nm)is prepared by the high-vacuum direct current(DC)magnetron sputtering.The effect of temperature on the spin valve structure and the magnetic properties are studied by x-ray diffraction(XRD),atomic force microscopy(AFM),and vibrating sample magnetometry.The effect of temperature on the exchange bias field thermomagnetic properties of multilayered spin valve is studied by the residence time of samples in a reverse saturation field.The results show that as the temperature increases,the IrMn(111)texture weakens,surface/interface roughness increases,and the exchange bias field decreases.Below 200℃,the exchange bias field decreases with the residence time increasing,and at the beginning of the negative saturation field,the exchange bias field Hex decreases first quickly and then slowly gradually.When the temperature is greater than 200℃,the exchange bias field is unchanged with the residence time increasing.展开更多
Molecular spintronics is an emerging field which evoked wide research attention since the first molecule-based spintronic device has been reported at 2002. Due to the active study over the last few years, it is found ...Molecular spintronics is an emerging field which evoked wide research attention since the first molecule-based spintronic device has been reported at 2002. Due to the active study over the last few years, it is found that the interfaces in spintronic device, so called spinterface, is of critical importance for many key issues in molecular spintronics, such as enhancing spin injection, lengthening spin transport distance, as well as manipulating spin signals in molecular spintronic devices. Here in this review, recent studies regarding spinterface in molecular devices, especially those impressive efforts devoted on spin manipulation, have been systematically summarized and discussed.展开更多
A new tamping device which is driven by an electrohydraulic exciter was proposed to overcome the limitations of mechanically driven devices.The double-rod oscillation cylinder drives the tamping arm to realize vibrati...A new tamping device which is driven by an electrohydraulic exciter was proposed to overcome the limitations of mechanically driven devices.The double-rod oscillation cylinder drives the tamping arm to realize vibration.A new spin valve was designed in order to fulfill dynamic state requirements of the oscillation cylinder.Parametric analysis was carried out by establishing mathematic model.Then,the relationships among the structure of valve port and the frequency,amplitude,output shock force of the cylinder were researched.An experimental device of the electrohydraulic exciter was established to validate the theoretical results.The signals were acquired by AVANT dynamic signal analyser of vibration.The results show that new tamping device can satisfy all kinds of complex working conditions with the flexible adjustment of frequency and amplitude.展开更多
Understanding the stability and current-carrying capacity of graphene spintronic devices is key to their applications in graphene channel-based spin current sensors,spin-torque oscillators,and potential spin-integrate...Understanding the stability and current-carrying capacity of graphene spintronic devices is key to their applications in graphene channel-based spin current sensors,spin-torque oscillators,and potential spin-integrated circuits.However,despite the demonstrated high current densities in exfoliated graphene,the current-carrying capacity of large-scale chemical vapor deposited(CVD)graphene is not established.Particularly,the grainy nature of chemical vapor deposited graphene and the presence of a tunnel barrier in CVD graphene spin devices pose questions about the stability of high current electrical spin injection.In this work,we observe that despite structural imperfections,CVD graphene sustains remarkably highest currents of 5.2×10^(8)A/cm^(2),up to two orders higher than previously reported values in multilayer CVD graphene,with the capacity primarily dependent upon the sheet resistance of graphene.Furthermore,we notice a reversible regime,up to which CVD graphene can be operated without degradation with operating currents as high as 108 A/cm^(2),significantly high and durable over long time of operation with spin valve signals observed up to such high current densities.At the same time,the tunnel barrier resistance can be modified by the application of high currents.Our results demonstrate the robustness of large-scale CVD graphene and bring fresh insights for engineering and harnessing pure spin currents for innovative device applications.展开更多
基金supported by the National Basic Research Program of China (2014CB921104)the National Natural Science Foundation of China (Grant Nos. 51222103, 11274113, 11474067, and 51171047)the support from the Program for New Century Excellent Talents in University (NCET-12-0132)
文摘The exchange-coupled [Co/Ni]N/Tb Fe nano-magnetic films can display strong perpendicular magnetic anisotropy(PMA) which depends on the Tb:Fe component ratio, Tb Fe layer thickness and the repetition number N of [Co/Ni]Nmultilayer. Perpendicular spin valves in the nano thickness scale, consisting of a [Co/Ni]3free and a [Co/Ni]5/Tb Fe reference multilayer, show high giant magnetoresistance(GMR) signal of 6.5 % and a large switching field difference over3 k Oe. However, unexpected slanting of the free layer magnetization, accompanied by a reduced GMR ratio, was found to be caused by the presence of a thick Fe-rich or even a thin but Tb-rich Tb Fe layer. We attribute this phenomenon to the large magnetostriction effect of Tb Fe which probably induces strong stress acting on the free layer and hence reduces its interfacial PMA.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11404013,11605003,61405003,11174020 and 11474012the Scientific Research Project of Beijing Educational Committee under Grant No KM201510011002the 2016 Graduate Research Program of Beijing Technology and Business University
文摘The extra heat generation in spin transport is usually interpreted in terms of the spin relaxation. Reformulating the heat generation rate, we find alternative current-force pairs without cross effects, which enable us to interpret the product of each pair as a distinct mechanism of heat generation. The results show that the spin-dependent part of the heat generation includes two terms. One is proportional to the square of the spin accumulation and arises from the spin relaxation. However, the other is proportional to the square of the spin-accumulation gradient and should be attributed to another mechanism, the spin diffusion. We illustrate the characteristics of the two mechanisms in a typical spin valve with a finite nonmagnetic spacer layer.
基金supported by the National Natural Science Foundation of China(Grant No.11547127)the China Postdoctoral Science Foundation(Grant No.2017M611852)the Natural Science Foundation for Colleges and Universities in Jiangsu Province,China(Grant No.13KJB140005)
文摘We propose two possible spin valves based on a zigzag silicene nanoribbon（ZSR） ferromagnetic junction. By using the Landauer–B u¨tikker formula, we calculate the spin-resolved conductance spectrum of the system and find that the spin transport is crucially dependent on the band structure of the ZSR tuned by a perpendicular electric field. When the ZSR is in the topological insulator phase under a zero electric field, the low-energy spin transport and its ON and OFF states in the tunneling junction mainly rely on the valley valve effect and the edge state of the energy band, which can be electrically modulated by the Fermi level, the spin–orbit coupling, and the local magnetization. When a nonzero perpendicular electric field is applied, the ZSR is a band insulator with a finite energy gap, the spin switch phenomenon is still preserved in the device and it does not come from the valley valve effect, but from the energy gap opened by the perpendicular electric field. The proposed device might be designed as electrical tunable spin valves to manipulate the spin degree of freedom of electrons in silicene.
基金the National Natural Science Foundation of China （Grant No. 10174014, 60271013, 10321003, 60490290） the State Key Project of Fundamental Research （No. 001CB610602 , 2002CB613504） the Hong Kong RGC Grant （HKUST6165/01P）.
文摘Top and bottom NiO-pinning spin valves of Si/Ta/NiO/Co/Cu/Co/Ta and Si/Ta/Co/Cu/Co/NiO/Ta were prepared by magnetron sputtering, and X-ray diffraction and giant magnetoresistance （GMR） ratio were measured in the temperature range from 5 to 300 K. For the bottom spin valve, the interracial roughness at NiO/Co is much smaller than that of Co/NiO in the top one. The Co/Cu and Cu/Co interfaces have the same roughness in the bottom and the top spin valves. NiO, Co, and Cu layers have （111） preferred orientations in the top one and random orientations in the bottom one. The GMR ratio of the bottom spin valve is larger than that of the top one at all temperatures and their difference increases with decreasing temperature.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11304381 and 11374244)the Research Funds of Renmin University of China(Grant No.17XNLF02)+1 种基金the Foundation for the Author of National Excellent Doctoral Dissertation of China(Grant No.201443)the Natural Science Foundation of Fujian Province of China(Grant No.2015J06016)
文摘Spin injection, spin diffusion, and spin detection are investigated in Co/Ag/Co lateral spin valves at room temperature.Clear spin accumulation signals are detected by the non-local measurement. By fitting the results to the one-dimensional diffusion equation,8.6% spin polarization of the Co/Ag interface and -180 nm spin diffusion length in Ag are obtained.Thermal treatment results show that the spin accumulation signal drastically decreases after 100℃ annealing, and disappears under 200℃ annealing. Our results demonstrate that, compared to the spin diffusion length, the decrease and the disappearance of the spin accumulation signal are mainly dominated by the variation of the interfacial spin polarization of the Co/Ag interface.
基金financially supported by the National Key Research and Development Program of China(grant no.2017YFA0207500)the National Natural Science Foundation of China(grant nos.51973153 and 11774254).
文摘Interface engineering in device fabrication is a significant but complicated issue.Although great successes have been achieved by conventional physical in situ or ex situ methods,it still suffers from complicated procedures.In this work,we present a facile method for fabricating phthalocyanine(Pc)-based two-dimensional conductive metal–organic framework(MOF)films.Based on PcM-Cu(M=Ni,Cu,H_(2))MOF films,spin valves with a vertical configuration of La_(0.67)Sr_(0.33)MnO_(3)/PcM-Cu MOFs/Co were constructed successfully,and exhibited notably high negative magnetoresistance(MR)up to -22% at 50 K.The penetrated Co atoms coordinated with the dehydrogenated hydroxy groups in the MOFs resulting in an antiferromagnetic layer of the PcM-Cu-Co hybrid structure.Interestingly,a significant exchange bias effect was demonstrated at the PcM-Cu MOF/Co interface,beneficial for the MR behavior.Thus,our present study provides new insights into developing high-performance organic spin valves via de novo molecular design.
基金The authors acknowledge financial support from the National Key R&D Program of China (Nos. 2016YFB0401100 and 2017YFA0204503)the National Natural Science Foundation of China (Nos. 52003190, 51633006, 91833306, 21875158, 51703159, and 51733004).
文摘Organic spin valve (OSV), one of the most promising and representative devices involving spin injection, transport and detection, has drawn tremendous attention owing to their ultra-long spin relaxation time in the field of molecular spintronics. Since the first demonstration of truly worked vertical OSV device in 2004, efforts in enhancement of high performance and pursuit of spin-related nature have been devoted in related field. It offers a new opportunity to develop the integrated flexible multi-functional arrays based on spintronics in the future. However, the unreliable working state in OSVs due to the lack of exploration on interface control will cause severe impact on the performance evaluation and further restrict their practical application. Herein, we focus on the recent progress in strategies for reliable fabrication and evaluation of typical OSVs in vertical configuration. Firstly, the challenges in protection of two spin interface properties and identification of spin-valve-like signals were proposed. Then, three points for attention including selection of bottom electrodes, optimization of organic spacer, and prevention of metal penetration to improve the device performance and reliability were mentioned. Particularly, various modified strategies to solve the “dead layer” issue were highlighted. Furthermore, we discussed the general protocols in the reliable evaluation of OSVs’ performance and transport mechanism identification. Notably, several key fundamentals resulting in spurious magnetoresistance (MR) response were illustrated. Finally, we also highlighted the future perspectives on spintronic devices of organic materials.
基金Supported by Open Project of Lab of Solid State Microstructures of Nanjing University (M06007)Doctoral Foundation of Hohai University (2084/40701117)Natural Science Foundation of Hohai University (2084/408307)
文摘Microstructure of NiO-containing Co/Cu/Co spin valves （CCC-SV） annealed at room temperature for nearly four years has been studied by synchrotron radiation X-ray diffraction. With the annealing time expanding, the thickness of each sub-layer remains nearly unchanged while the interface roughness varies obviously compared with that of samples without annealing. The roughness at the interface of NiO/Co decreases with the annealing time increasing for both of the samples with NiO layer on the top （TSV） and under the bottom （BSV） of CCC-SV. On the other hand, the roughness at Co/Cu interface increases with the annealing time expanding for BSV while it decreases for TSV. These results indicate that the structure of TSV is more stable than that of BSV.
基金financially supported by the National Natural Science Foundation of China (Nos. 11174020, 51331002, and 51371027)the Fundamental Research Funds for the Central Universities FRF-SD-12-011A
文摘Pseudo spin valves（SVs） exhibiting perpendicular magnetic anisotropy were prepared by magnetron sputtering. Magnetization measurements of the Co/Pt multilayers were performed to select the reference and free layers. The selection criteria are square magnetic hysteresis loops, weaker current shunting effect, and proper coercivity. The optimal reference layer and free layer are Pt（5.0 nm）/[Co（0.4 nm）/Pt（0.6 nm）]3/Co（0.4 nm）/Cu（3.0 nm）and Cu（3.0 nm）/[Co（0.4 nm）/Pt（1.5 nm）]4, respectively.The resulting pseudo SV exhibits two well-separated hysteresis loops when the field is applied perpendicular to the film plane. The minor hysteresis loop corresponding to the free layer shifts toward negative direction of the magnetic field axis, indicating ferromagnetic interlayer exchange coupling between the two magnetic layers. The coupling also enhances the coercivity（HC） of both layers. The perpendicular giant magnetoresistance（GMR） of 2.7 % is achieved with current in plane measurement. The GMR first increases when Pt seed layer is thickened, reaches a maximum of 3.0 % at 4 nm and then decreases with the further increase of thickness. But thicker Cu spacer layer always lowers the GMR of the SV.
基金supported by the National Key R&D Program of China (2017YFA0303400 and 2017YFB0405700)the National Natural Science foundation of China (61774144)+2 种基金Beijing Natural Science Foundation Key Program (Z190007)the Project from Chinese Academy of Sciences (QYZDY-SSW-JSC020, XDPB12, and XDB28000000)K C Wong Education Foundation。
文摘Different than covalently bonded magnetic multilayer systems,high-quality interfaces without dangling bonds in van der Waals(vd W)junctions of two-dimensional(2D)layered magnetic materials offer opportunities to realize novel functionalities.Here,we report the fabrication of multi-state vertical spin valves without spacer layers by using vd W homo-junctions in which exfoliated Fe3GeTe2 nanoflakes act as ferromagnetic electrodes and/or interlayers.We demonstrate the typical behavior of two-state and threestate magnetoresistance for devices with two and three Fe3GeTe2 nanoflakes,respectively.Distinct from traditional spin valves with sandwich structures,our novel homo-junction-based spin-valve structure allows the straightforward realization of multi-state magnetic devices.Our work demonstrates the possibility of extend multi-state,non-volatile spin information to 2 D magnetic homo-junctions,and it emphasizes the utility of vd W interface as a fundamental building block for spintronic devices.
基金the National Natural Science Foundation of China(61674116,51873148,51633006,and 52003190)the Ministry of Science and Technology of China(2016YFA0202302)the Natural Science Foundation of Tianjin(18JC-YBJC18400)。
文摘Single crystals of organic semiconductors with perfect crystal structure and minimal density of defects can exhibit high mobility and low spin scattering compared with their amorphous or polycrystalline counterparts.Therefore,these materials are promising candidates as the spin transport media to obtain long spin relaxation times and spin diffusion lengths in spintronic devices.However,the investigation of spin injection and transport properties in organic single crystals is hindered by the inability to construct devices such as single-crystalline organic spin valves(OSVs).Herein,thin and large organic single crystals of 6,13-bis(triisopropylsilylethynyl)pentacene(TIPS-pentacene)were grown on a liquid substrate and transferred to a target substrate carrying ferromagnetic electrodes to construct single-crystalline OSVs.The magnetoresistance(MR)responses of the single crystals were investigated to study their spin injection and transport properties.MR value as high as 17%was probed with an intermediate layer thickness of 269 nm.More importantly,spin transport was still observed in a single crystal of a thickness up to 457 nm,which was much larger than that of polycrystalline thin film.Our research provides a general methodology for constructing single-crystalline OSVs and paves the way to probe the intrinsic spin transport properties of organic semiconductors based on single crystals.
基金financially supported by the National Natural Science Foundation of China(Nos.11304381 and 11174366)the Research Funds of Renmin University of China(No.13XNLF02)
文摘The spin transport was investigated in permally （Py）/MgO/Ag junction with lateral spin valve structure. Non-local lateral spin valves measurement was carried out to determin, the apin accumulignal in Ag strip, and the spin dif u^sion - length in Ag of the lateral spin valves was extracted from devices with the different distances between injector and detector. The experimental results are found that spin accumulation and spin diffusion length （2s） could be significantly enhanced in Ag strip with MgO capping layer, and those effects may be attributed to the low-surface spin scattering rate in Ag with an MgO cap- ping layer.
基金This project was primarily supported by the National Science Foundation through the Nebraska Materials Research Science and Engineering Center(Grant No.DMR-1420645).
文摘Magnetoelectric coupling has been a trending research topic in both organic and inorganic materials and hybrids.The concept of controlling magnetism using an electric field is particularly appealing in energy efficient applications.In this spirit,ferroelectricity has been introduced to organic spin valves to manipulate the magneto transport,where the spin transport through the ferromagnet/organic spacer interfaces(spinterface)are under intensive study.The ferroelectric materials in the organic spin valves provide a knob to vary the interfacial energy alignment and the interfacial crystal structures,both are critical for the spin transport.In this review,we introduce the recent efforts of controlling magnetoresistance of organic spin valves using ferroelectricity,where the ferroelectric material is either inserted as an interfacial layer or used as a spacer material.The realization of the ferroelectric control of magneto transport in organic spin valve,advances our understanding in the spin transport through the ferromagnet/organic interface,and suggests more functionality of organic spintronic devices.
基金performed within the framework of State Assignment from the Ministry of Education and Science of Russian Federation (topic Spin, No. 122021000036-3 and topic Magnet, No. 122021000034-9)partially supported by the Russian Foundation for Basic Research (project No. 2042-660018)。
文摘Flexible spin valves were prepared by magnetron sputtering on polyimide substrates. The buffer layer that reduces significantly the effect of the polymer substrate on the spin valve microstructure and magnetoresistive properties was revealed. Bending deformation was applied to the microobjects based on the flexible spin valves in parallel to anisotropy axes. It was revealed that during the bend the magnetoresistance changes due to the joint impact of both the change of the magnetic field projection on the film plane and the change of the magnetic properties of the ferromagnetic layers. The obtained dependences have been used in construction of bending sensor, in which the flexible spin valve microstripes were united into the Wheatstone bridge.
基金supported by the National Natural Science Foundation of China(Grant No.11404322)the Natural Science Foundation of Huai’an(Grant Nos.HAB202229 and HAB202150)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.22KJD140002)。
文摘A single-molecule magnet is a long-sought-after nanoscale component because it can enable us to miniaturize nonvolatile memory storage devices.The signature of a single-molecule magnet is switching between two bistable magnetic ground states under an external magnetic field.Based on this feature,we theoretically investigate a magnetic-fieldcontrolled reversible resistance change active at low temperatures in a molecular magnetic tunnel junction,which consists of a single-molecule magnet sandwiched between a ferromagnetic electrode and a normal metal electrode.Our numerical results demonstrate that the molecular magnetism orientation can be manipulated by magnetic fields to be parallel/antiparallel to the ferromagnetic electrode magnetization.Moreover,different magnetic configurations can be“read out”based on different resistance states or different spin polarization parameters in the current spectrum,even in the absence of a magnetic field.Such an external magnetic field-controlled resistance state switching effect is similar to that in traditional spin valve devices.The difference between the two systems is that one of the ferromagnetic layers in the original device has been replaced by a magnetic molecule.This proposed scheme provides the possibility of better control of the spin freedom of electrons in molecular electrical devices,with potential applications in future high-density nonvolatile memory devices.
基金financially supported by the National Natural Science Foundation of China (Nos. 61025021and 60936002)the National Key Project of Scienceand Technology of China (Nos. 2009ZX02023-001-3 and 2011ZX02403-002)the Independent Scientific Research of Tsinghua University (No. 2010THZ0)
文摘The magnetoresistance behavior and the magnetization reversal mode of NiFe/Cu/CoFe/IrMn spin valve giant magnetoresistance （SV-GMR） in nanoscale were investigated experimentally and theoretically by nanosized magnetic simulation methods. Based on the Landau-Lifshitz-Gilbert equation, a model with a special gridding was proposed to calculate the giant magnetoresistance ratio （MR） and investigate the magnetization reversal mode. The relationship between MR and the external magnetic field was obtained and analyzed. Studies into the variation of the magnetization distribution reveal that the magnetization reversal mode, that is, the jump variation mode for NiFe/Cu/CoFe/IrMn, depends greatly on the antiferromagnetic coupling behavior between the pinned layer and the antiferromagnetic layer. It is also found that the switching field is almost linear with the exchange coefficient.
基金supported by the Yunnan Provincial Ten Thousand Talents Plan Young Talents Training Fund,China(Grant No.KKRD201952029)the Applied Basic Research Program of Yunnan Province,China(Grant No.2011FB037)the School Talent Cultivation Foundation,China(Grant No.KKSY201252017)。
文摘A multilayered spin valve film with a structure of Ta(5 nm)/Co_(75)Fe_(25)(5 nm)/Cu(2.5 nm)/Co_(75)Fe_(25)(5 nm)/Ir_(20)Mn_(80)(12 nm)/Ta(8 nm)is prepared by the high-vacuum direct current(DC)magnetron sputtering.The effect of temperature on the spin valve structure and the magnetic properties are studied by x-ray diffraction(XRD),atomic force microscopy(AFM),and vibrating sample magnetometry.The effect of temperature on the exchange bias field thermomagnetic properties of multilayered spin valve is studied by the residence time of samples in a reverse saturation field.The results show that as the temperature increases,the IrMn(111)texture weakens,surface/interface roughness increases,and the exchange bias field decreases.Below 200℃,the exchange bias field decreases with the residence time increasing,and at the beginning of the negative saturation field,the exchange bias field Hex decreases first quickly and then slowly gradually.When the temperature is greater than 200℃,the exchange bias field is unchanged with the residence time increasing.
基金Project supported by the National Natural Science Foundation of China(Grant No.21673059)the Funds from Ministry of Science and Technology of China(Grant Nos.2017YFA0206600 and 2016YFA0200700)+1 种基金the Instrument Development Project of Chinese Academy of Sciences(Grant No.YJKYYQ20170037)the CAS Pioneer Hundred Talents Program
文摘Molecular spintronics is an emerging field which evoked wide research attention since the first molecule-based spintronic device has been reported at 2002. Due to the active study over the last few years, it is found that the interfaces in spintronic device, so called spinterface, is of critical importance for many key issues in molecular spintronics, such as enhancing spin injection, lengthening spin transport distance, as well as manipulating spin signals in molecular spintronic devices. Here in this review, recent studies regarding spinterface in molecular devices, especially those impressive efforts devoted on spin manipulation, have been systematically summarized and discussed.
基金Projects(50975252,51275499)supported by the National Natural Science Foundation of ChinaProject(2013CB035404)supported by the National Basic Research Program of ChinaProject(GZKF-201312)supported by Open Foundation of the State Key Laboratory of Fluid Power Transmission and Control,China
文摘A new tamping device which is driven by an electrohydraulic exciter was proposed to overcome the limitations of mechanically driven devices.The double-rod oscillation cylinder drives the tamping arm to realize vibration.A new spin valve was designed in order to fulfill dynamic state requirements of the oscillation cylinder.Parametric analysis was carried out by establishing mathematic model.Then,the relationships among the structure of valve port and the frequency,amplitude,output shock force of the cylinder were researched.An experimental device of the electrohydraulic exciter was established to validate the theoretical results.The signals were acquired by AVANT dynamic signal analyser of vibration.The results show that new tamping device can satisfy all kinds of complex working conditions with the flexible adjustment of frequency and amplitude.
基金the European Research Council(ERC)Project SPINNER,Swedish Research Council(VR Starting Grants 2016-03278,2017-05030,as well as project grant 2021-03675)Stiftelsen Olle Engkvist Byggmästare(No.200-0602)+2 种基金Energimyndigheten(No.48698-1)Formas(No.2019-01326)Wenner-Gren Stiftelserna(Nos.UPD2018-0003 and UPD2019-0166).
文摘Understanding the stability and current-carrying capacity of graphene spintronic devices is key to their applications in graphene channel-based spin current sensors,spin-torque oscillators,and potential spin-integrated circuits.However,despite the demonstrated high current densities in exfoliated graphene,the current-carrying capacity of large-scale chemical vapor deposited(CVD)graphene is not established.Particularly,the grainy nature of chemical vapor deposited graphene and the presence of a tunnel barrier in CVD graphene spin devices pose questions about the stability of high current electrical spin injection.In this work,we observe that despite structural imperfections,CVD graphene sustains remarkably highest currents of 5.2×10^(8)A/cm^(2),up to two orders higher than previously reported values in multilayer CVD graphene,with the capacity primarily dependent upon the sheet resistance of graphene.Furthermore,we notice a reversible regime,up to which CVD graphene can be operated without degradation with operating currents as high as 108 A/cm^(2),significantly high and durable over long time of operation with spin valve signals observed up to such high current densities.At the same time,the tunnel barrier resistance can be modified by the application of high currents.Our results demonstrate the robustness of large-scale CVD graphene and bring fresh insights for engineering and harnessing pure spin currents for innovative device applications.
