We fabricated flexible spin valves on polyvinylidene fluoride（PVDF） membranes and investigated the influence of thermal deformation of substrates on the giant magnetoresistance（GMR） behaviors. The large magnetostr...We fabricated flexible spin valves on polyvinylidene fluoride（PVDF） membranes and investigated the influence of thermal deformation of substrates on the giant magnetoresistance（GMR） behaviors. The large magnetostrictive Fe_（81）Ga_（19）（Fe Ga） alloy and the low magnetostrictive Fe_（19）Ni_（81）（Fe Ni） alloy were selected as the free and pinned ferromagnetic layers.In addition, the exchange bias（EB） of the pinned layer was set along the different thermal deformation axes α_（31） or α_（32） of PVDF. The GMR ratio of the reference spin valves grown on Si intrinsically increases with lowering temperature due to an enhancement of spontaneous magnetization. For flexible spin valves, when decreasing temperature, the anisotropic thermal deformation of PVDF produces a uniaxial anisotropy along the α_（32） direction, which changes the distribution of magnetic domains. As a result, the GMR ratio at low temperature for spin valves with EB α_（32）becomes close to that on Si, but for spin valves with EB α_（31）is far away from that on Si. This thermal effect on GMR behaviors is more significant when using magnetostrictive Fe Ga as the free layer.展开更多
Ni-Fe/Cu/Co/Cu multilayered nanowire arrays were electrodeposited into anodic aluminum oxide template by using dual-bath method at room temperature. Scanning electron microscopy and transmission electron microscopy we...Ni-Fe/Cu/Co/Cu multilayered nanowire arrays were electrodeposited into anodic aluminum oxide template by using dual-bath method at room temperature. Scanning electron microscopy and transmission electron microscopy were used to characterize the morphology and structure of the multilayered nanowire arrays. Vibrating sample magnetometer and physical property measurement system were used to measure their magnetic and giant magnetoresistance （GMR） properties. The effect of sub-layer thickness on the magnetic and GMR properties was investigated. The results indicate that magnetic properties of electmdeposited nanowires are not affected obviously by Cu layer thickness, while magnetic layers （Ni-Fe and Co layers） have significant influence. In addition, GMR ratio presents an oscillatory behavior as Cu layer thickness changes. The magnetic and GMR properties of the multilayered nanowire arrays are optimum at room temperature for the material structure of Ni-Fe （25 nm）/Cu （15 nm）/Co （25 nm）/Cu （15 nm） with 30 deposition cycles.展开更多
The giant magnetoresistance (GMR) in magnetic multilayers with current in the plane of the layers is studied by using the quantum-statistical Green's function approach, in which the effects of the interfacial roug...The giant magnetoresistance (GMR) in magnetic multilayers with current in the plane of the layers is studied by using the quantum-statistical Green's function approach, in which the effects of the interfacial roughness and magnetization configuration on the GMR are included. It is shown that the maximal GMR first increases and then decreases with increasing interfacial roughness, exhibiting a peak at an optimum value of interfacial roughness. An approximately linear dependence of GMR on is obtained, where is the angle between magnetizations of the two successive ferromagnetic layers. Furthermore, the maximal GMR is found to increase with increasing the number of bilayers.展开更多
GMR effect of multilayers of bcc-Fe(M)(M=Co, Ni) alloy and Cu layers has been investigated. The maximum MR ratio is found at 1.1 nm Fe(Co) and 1.3～1.4 nm Cu layer thickness in [Fe(Co)/CuJ, and at 1.6 nm Fe(Ni) and 1....GMR effect of multilayers of bcc-Fe(M)(M=Co, Ni) alloy and Cu layers has been investigated. The maximum MR ratio is found at 1.1 nm Fe(Co) and 1.3～1.4 nm Cu layer thickness in [Fe(Co)/CuJ, and at 1.6 nm Fe(Ni) and 1.4 nm Cu layer thickness in [Fe(Ni)/Cu]. Under the optimum annealing condition, the MR ratio increases up to 50% and 38% for Fe(Co) and Fe(Ni) systems, respectively. The origin of the increase of GMR is discussed, taking the progress of preferred orientation of Fe(Co)[100] or Fe(Ni)[100] by anneahng into account.展开更多
We have studied the transport property of the composites （La0.83Sr0.17 MnO3）1-x（ITO）x [ITO=（In2O3）0.95 （SNO2）0.05], which were fabricated by mechanically mixing La0.83Sr0.17MnO3 and ITO grains. A giant positiv...We have studied the transport property of the composites （La0.83Sr0.17 MnO3）1-x（ITO）x [ITO=（In2O3）0.95 （SNO2）0.05], which were fabricated by mechanically mixing La0.83Sr0.17MnO3 and ITO grains. A giant positive magnetoresistance （PMR） has been observed above the Curie temperature Tc for samples with x around 0.40, in addition to the negative magnetoresistanee related to spin-dependent interracial tunnelling below To. For （La0.83Sr0.17MnO3）0.6（ITO）0.4, the magnetoresistive ratio for the PMR can reach 39.3% under a magnetic field H=2.24×10^5A/m. Theoretical analysis suggests that the magnetic-field-induced broadening of the p-n barrier between both kinds of grains and the density of the p-n heterostructures should be responsible for the PMR behaviour.展开更多
Taking into account the quantum size effects and considering three types of scattering from bulk impurities,rough surface and rough interfaces, we use quantum-statistical Green's function approach and Kubo theory ...Taking into account the quantum size effects and considering three types of scattering from bulk impurities,rough surface and rough interfaces, we use quantum-statistical Green's function approach and Kubo theory to calculate the electronic conductivity and the giant magnetoresistance in magnetic multilayered cylindrical systems. It is found that in the limit of weakly scattering from impurities surface and interfaces, the total conductivity is given by a sum of conductivities of all the subbands and two spin-channels. For each subband and each spin-channel the scattering rate due to the impurities, surface and interfaces is added up.展开更多
A special Fe3O4nanoparticles–graphene（Fe3O4–GN） composite as a magnetic label was employed for biodetection using giant magnetoresistance（GMR） sensors with a Wheatstone bridge. The Fe3O4–GN composite exhibits a...A special Fe3O4nanoparticles–graphene（Fe3O4–GN） composite as a magnetic label was employed for biodetection using giant magnetoresistance（GMR） sensors with a Wheatstone bridge. The Fe3O4–GN composite exhibits a strong ferromagnetic behavior with the saturation magnetization MS of approximately 48 emu/g, coercivity HC of 200 Oe, and remanence Mr of 8.3 emu/g, leading to a large magnetic fringing field. However, the Fe3O4 nanoparticles do not aggregate together, which can be attributed to the pinning and separating effects of graphene sheet to the magnetic particles. The Fe3O4–GN composite is especially suitable for biodetection as a promising magnetic label since it combines two advantages of large fringing field and no aggregation. As a result, the concentration x dependence of voltage difference ｜？V｜ between detecting and reference sensors undergoes the relationship of ｜？V｜ = 240.5 lgx ＋ 515.2 with an ultralow detection limit of 10 ng/mL（very close to the calculated limit of 7 ng/mL） and a wide detection range of 4 orders.展开更多
Prx（Co40Ag60）100-x （x=0, 0.5, 1, 1.5, 2, 3） granular films have been prepared by DC magneto controlled sputtering method. The XRD data indicated that Pr element favors the （111） plane preferential orientation. M...Prx（Co40Ag60）100-x （x=0, 0.5, 1, 1.5, 2, 3） granular films have been prepared by DC magneto controlled sputtering method. The XRD data indicated that Pr element favors the （111） plane preferential orientation. Magnetic measurements indicate that the average size of magnetic particles decreases as Pr content increases. For relatively low addition of Pr to CoAg granular films, Pr element can enhance GMR value and a peak value of about -14.3% is obtained at x=1.展开更多
The structure and microfabrication,the detecting theory and the way of biomolecular recognition device based on giant magnetoresistance(GMR) effect are introduced,also the signal detecting and processing instrumentati...The structure and microfabrication,the detecting theory and the way of biomolecular recognition device based on giant magnetoresistance(GMR) effect are introduced,also the signal detecting and processing instrumentation are presented. Here the GMR biosensor was fabricated with magnetic tunnel junction(MJT) material.The biomolecular recognition device contains an array of MJT sensors,single MJT sensor size is 10μm×20μm,tunneling magnetoresistance ratio(TMR) at room temperature is 52.2%,the typical values of junction resistance-area product Rs is 2.6 kΩμm^2,detecting sensitivity of this system is about 8×10^(-4) A·m^(-1).Bioadaptation layer of this device was fabricated with PDMS the thickness of which is less than 100 nm.展开更多
A phenomenological theoretical model for magnetic multilayer based on Boltzmann equation and Fuchs-Sondheimer theory is studied. An oscillatory transmission coefficient (Ts) is introduced into the boundary conditions ...A phenomenological theoretical model for magnetic multilayer based on Boltzmann equation and Fuchs-Sondheimer theory is studied. An oscillatory transmission coefficient (Ts) is introduced into the boundary conditions to simulate the alternate ferromagnetic and anti-ferromagnetic coupling between the magnetic layers. The transmission coefficient has an oscillatory factor relating to the thickness of space layer. Other effects such as interface roughness on Ts are also taken into account. The numerical results for [Fe/Cr]n multilayer agree with the experimental data very well, both in the period and range of osciallation, which is leaded by the dependence of giant magnetoresistance(GMR) on layer thickness of space layer.展开更多
With the discovery of giant magnetoresistance(GMR),research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials and/or artificial structures,which has lead...With the discovery of giant magnetoresistance(GMR),research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials and/or artificial structures,which has lead to the idea of spintronics.A brief introduction is given to GMR effects from scientific background to experimental observations and theoretical models.In addition,the mechanisms of various magnetoresistance beyond the GMR are reviewed,for instance,tunnelling magnetoresistance,colossal magnetoresistance,and magnetoresistance in ferromagnetic semiconductors,nanowires,organic spintronics and non-magnetic systems.展开更多
The atomic structure of quasi one-dimensional(1D) van der Waals materials can be regarded as the stacking of atomic chains to form thin flakes or nanoribbons, which substantially differentiates them from typical two-d...The atomic structure of quasi one-dimensional(1D) van der Waals materials can be regarded as the stacking of atomic chains to form thin flakes or nanoribbons, which substantially differentiates them from typical two-dimensional(2D) layered materials and 1D nanotube/nanowire array. Here we present our studies on quasi 1D gold selenide(AuSe) that possesses highly anisotropic crystal structure, excellent electrical conductivity, giant magnetoresistance, and unusual reentrant metallic behavior. The low inplane symmetry of AuSe gives rise to its high anisotropy of vibrational behavior. In contrast, quasi 1D AuSe exhibits high in-plane electrical conductivity along the directions of both atomic chains and perpendicular one, which can be understood as a result of strong interchain interaction. We found that AuSe exhibits a near quadratic nonsaturating giant magnetoresistance of 1841% with the magnetic field perpendicular to its in-plane. We also observe unusual reentrant metallic behavior, which is caused by the carrier mismatch in the multiband transport. Our works help to establish fundamental understandings on quasi 1D van der Waals semimetallic AuSe and identify it as a new candidate for exploring giant magnetoresistance and compensated semimetals.展开更多
Recent studies on the electrical switching of tetragonal antiferromagnet(AFM)via Neél spin-orbit torque have paved the way for the economic use of antiferromagnetic materials.The most difficult obstacle that pres...Recent studies on the electrical switching of tetragonal antiferromagnet(AFM)via Neél spin-orbit torque have paved the way for the economic use of antiferromagnetic materials.The most difficult obstacle that presently limits the application of antiferromagnetic materials in spintronics,especially in memory storage applications,could be the small and fragile magnetoresistance(MR)in the AFM-based nanostructure.In this study,we investigated the spin transports in Mn2Au-based tunnel junctions based on the first-principle scattering theory.Giant MRs more than 1000%are predicted in some Fe/MgO/Ag/Mn2Au/Ta junctions that are about the same order as that in an MgO-based ferromagnetic tunnel junction with same barrier thickness.The interplay of the spin filtering effect,the quantum well resonant states,and the interfacial resonant states could be responsible for the unusual giant and robust MRs observed in these Mn2Au-based junctions.展开更多
Magnetoresistanoe in the temperature region from 300 K to liquid helium temperature has been measured on good (100) oriented La2/3Ca1/3MnO2 thin films prepared by d.c. magnetron sputtering on ZrO2 (100) substrates. It...Magnetoresistanoe in the temperature region from 300 K to liquid helium temperature has been measured on good (100) oriented La2/3Ca1/3MnO2 thin films prepared by d.c. magnetron sputtering on ZrO2 (100) substrates. It is found that there appears a resistance peak at about TP = 72K at zero magnetic field, and this peak moves to higher temperature with increasing field H, and R decreases simultaneously. However, the magnetoresistance ratio MR = 5R /R (H) = (Ro~ RH) /RH has a different temperature dependence. There are also MR peaks, but the temperature of maximum MR is at about 25 K which does not change with changing external magnetic field. The heat treatment (annealed at 700C in 105’Pa O2 for 30min) will make R reduce dramatically and has an effect on the temperature dependence of R and its MR.展开更多
The transport property of electrons tunneling through arrays of magnetic and electric barriers is studied in silicene. In the tunneling transmission spectrum, the spin-valley-dependent filtered states can be achieved ...The transport property of electrons tunneling through arrays of magnetic and electric barriers is studied in silicene. In the tunneling transmission spectrum, the spin-valley-dependent filtered states can be achieved in an incident energy range which can be controlled by the electric gate voltage. For the parallel magnetization configuration, the transmission is asymmetric with respect to the incident angle θ, and electrons with a very large negative incident angle can always transmit in propagating modes for one of the spin-valley filtered states under a certain electromagnetic condition. But for the antiparallel configuration, the transmission is symmetric about θ and there is no such transmission channel. The difference of the transmission between the two configurations leads to a giant tunneling magnetoresistance （TMR） effect. The TMR can reach to 100% in a certain Fermi energy interval around the electrostatic potential. This energy interval can be adjusted significantly by the magnetic field and/or electric gate voltage. The results obtained may be useful for future valleytronic and spintronic applications, as well as magnetoresistance device based on silicene.展开更多
Granular CoxCu1-x alloy films were prepared by electrodeposition at room temperature directly onto semiconducting Si substrate. X-ray diffraction (XRD) revealed that the as-deposited films formed single phase metastab...Granular CoxCu1-x alloy films were prepared by electrodeposition at room temperature directly onto semiconducting Si substrate. X-ray diffraction (XRD) revealed that the as-deposited films formed single phase metastable fcc alloy structure. The fcc lattice parameter α was found to decrease linearly with increasing Co concentration x in the studied range. The giant magnetoresistance (GMR) of the films was improved after annealing. Pure Co fcc diffraction peaks were observed in the diffractogram of the annealed sample, indicating phase separation occurred upon annealing. The optimal annealing temperature was 450℃. The maximum of magnetoresistance (MR) ratio 8.21% was obtained for the Co20Cu80 thin film after annealing at 450℃ for 1 h. The saturation field decreased upon annealing in the MR curves of Co20Cu80 film.展开更多
Thickness effects of thin La0.7Sr0.3MnO3 （LSMO） films on （LaAlOa）0.3（Sr2AlTaO6）0.7 substrates were examined by a slow positron beam technique. Doppler-broadening line shape parameter S was measured as a function...Thickness effects of thin La0.7Sr0.3MnO3 （LSMO） films on （LaAlOa）0.3（Sr2AlTaO6）0.7 substrates were examined by a slow positron beam technique. Doppler-broadening line shape parameter S was measured as a function of thickness and differnt annealing conditions. Results reveal there could be more than one mechanism to induce vacancy-like defects. It was found that strain-induced defects mainly influence the S value of the in situ oxygenambience annealing LSMO thin films and the strain could vanish still faster along with the increase of thickness, and the oxygen-deficient induced defects mainly affect the S value of post-annealing LSMO films.展开更多
The quantum phenomenological model has been proposed to investigate the magnetic property of nanometer magnetic granular film in an applied magnetic field.The magnetoresistance of the granular films with two distinct ...The quantum phenomenological model has been proposed to investigate the magnetic property of nanometer magnetic granular film in an applied magnetic field.The magnetoresistance of the granular films with two distinct magnetic phases has been calculated by using Born approximation.The results show that the average scattering cross section of the magnetic cluster decreases with the increasing number n of the atom.The origin of the giant magnetoresistance comes from the spin dependent scattering between conduction electrons and magnetic granules and the field dependence of magnetoresistance and the quadratic relation of magnetoresistance on the rate of magnetic moment are in good agreement with the experiments reported.展开更多
Our recent research on the Mn-based antiperovskite functional materials AXMn3 （A： metal or semiconducting elements; X： C or N） is outlined. Antiperovskite carbides （e.g., AlCMn3） show large magnetocaloric effect...Our recent research on the Mn-based antiperovskite functional materials AXMn3 （A： metal or semiconducting elements; X： C or N） is outlined. Antiperovskite carbides （e.g., AlCMn3） show large magnetocaloric effect comparable to those of typical magnetic refrigerant materials. Enhanced giant magnetoresistance up to 70% at 50 kOe （1 Oe=79.5775 A.m-1） over a wide temperature span was obtained in Ga1-xZnxCMn3 and GaCMn3 xNix. In Cu0.3Sn0.5NMn3.2, negative thermal expansion （NTE） was achieved in a wide temperature region covering room temperature （α = -6.8 ppm/K, 150 K-40 K）. Neutron pair distribution function analysis suggests the Cu/Sn-Mn bond fluctuation is the driving force for the NTE in Cu1- xSnxNMn3. In CuN1- xCxMn3 and CuNMn3 yCoy, the temperature coefficient of resistivity （TCR） decreases monotonically from positive to negative as Co or C content increases. TCR is extremely low when the composition approaches the critical points. For example, TCR is - 1.29 ppm/K between 240 K and 320 K in CuN0.95C0 05Mn3, which is one twentieth of that in the typical low-TCR materials （- 25 ppm/K）. By studying the critical scaling behavior and X deficiency effect, some clues of localized-electron magnetism have been found against the background of electronic itinerant magnetism.展开更多
Considering the special carriers in organic semiconductors, the spin polarized current under electric field in a ferromagnetic/organic semiconductor system is theoretically studied. Based on the spin-diffusion theory,...Considering the special carriers in organic semiconductors, the spin polarized current under electric field in a ferromagnetic/organic semiconductor system is theoretically studied. Based on the spin-diffusion theory, the current spin polarization under the electric field is obtained. It is found that electric field can enhance the current spin polarization.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11374312,51401230,51522105,and 51471101)the Ningbo Science and Technology Innovation Team,China(Grant No.2015B11001)
文摘We fabricated flexible spin valves on polyvinylidene fluoride（PVDF） membranes and investigated the influence of thermal deformation of substrates on the giant magnetoresistance（GMR） behaviors. The large magnetostrictive Fe_（81）Ga_（19）（Fe Ga） alloy and the low magnetostrictive Fe_（19）Ni_（81）（Fe Ni） alloy were selected as the free and pinned ferromagnetic layers.In addition, the exchange bias（EB） of the pinned layer was set along the different thermal deformation axes α_（31） or α_（32） of PVDF. The GMR ratio of the reference spin valves grown on Si intrinsically increases with lowering temperature due to an enhancement of spontaneous magnetization. For flexible spin valves, when decreasing temperature, the anisotropic thermal deformation of PVDF produces a uniaxial anisotropy along the α_（32） direction, which changes the distribution of magnetic domains. As a result, the GMR ratio at low temperature for spin valves with EB α_（32）becomes close to that on Si, but for spin valves with EB α_（31）is far away from that on Si. This thermal effect on GMR behaviors is more significant when using magnetostrictive Fe Ga as the free layer.
基金Supported by the Natural Science Foundation of Tianjin,China(08JCZDJC17400)
文摘Ni-Fe/Cu/Co/Cu multilayered nanowire arrays were electrodeposited into anodic aluminum oxide template by using dual-bath method at room temperature. Scanning electron microscopy and transmission electron microscopy were used to characterize the morphology and structure of the multilayered nanowire arrays. Vibrating sample magnetometer and physical property measurement system were used to measure their magnetic and giant magnetoresistance （GMR） properties. The effect of sub-layer thickness on the magnetic and GMR properties was investigated. The results indicate that magnetic properties of electmdeposited nanowires are not affected obviously by Cu layer thickness, while magnetic layers （Ni-Fe and Co layers） have significant influence. In addition, GMR ratio presents an oscillatory behavior as Cu layer thickness changes. The magnetic and GMR properties of the multilayered nanowire arrays are optimum at room temperature for the material structure of Ni-Fe （25 nm）/Cu （15 nm）/Co （25 nm）/Cu （15 nm） with 30 deposition cycles.
文摘The giant magnetoresistance (GMR) in magnetic multilayers with current in the plane of the layers is studied by using the quantum-statistical Green's function approach, in which the effects of the interfacial roughness and magnetization configuration on the GMR are included. It is shown that the maximal GMR first increases and then decreases with increasing interfacial roughness, exhibiting a peak at an optimum value of interfacial roughness. An approximately linear dependence of GMR on is obtained, where is the angle between magnetizations of the two successive ferromagnetic layers. Furthermore, the maximal GMR is found to increase with increasing the number of bilayers.
基金Ministry of Education, Science, Sports and Culture under Grantin-Aid for Scielltific Research on Priority Areas (A), Japan!(No.
文摘GMR effect of multilayers of bcc-Fe(M)(M=Co, Ni) alloy and Cu layers has been investigated. The maximum MR ratio is found at 1.1 nm Fe(Co) and 1.3～1.4 nm Cu layer thickness in [Fe(Co)/CuJ, and at 1.6 nm Fe(Ni) and 1.4 nm Cu layer thickness in [Fe(Ni)/Cu]. Under the optimum annealing condition, the MR ratio increases up to 50% and 38% for Fe(Co) and Fe(Ni) systems, respectively. The origin of the increase of GMR is discussed, taking the progress of preferred orientation of Fe(Co)[100] or Fe(Ni)[100] by anneahng into account.
基金Project supported by the National Natural Science Foundation of China （Grant No 20473038）, the Foundation of High-Tech Project in Jiangsu province, China （Grant No BG-2005401）.
文摘We have studied the transport property of the composites （La0.83Sr0.17 MnO3）1-x（ITO）x [ITO=（In2O3）0.95 （SNO2）0.05], which were fabricated by mechanically mixing La0.83Sr0.17MnO3 and ITO grains. A giant positive magnetoresistance （PMR） has been observed above the Curie temperature Tc for samples with x around 0.40, in addition to the negative magnetoresistanee related to spin-dependent interracial tunnelling below To. For （La0.83Sr0.17MnO3）0.6（ITO）0.4, the magnetoresistive ratio for the PMR can reach 39.3% under a magnetic field H=2.24×10^5A/m. Theoretical analysis suggests that the magnetic-field-induced broadening of the p-n barrier between both kinds of grains and the density of the p-n heterostructures should be responsible for the PMR behaviour.
文摘Taking into account the quantum size effects and considering three types of scattering from bulk impurities,rough surface and rough interfaces, we use quantum-statistical Green's function approach and Kubo theory to calculate the electronic conductivity and the giant magnetoresistance in magnetic multilayered cylindrical systems. It is found that in the limit of weakly scattering from impurities surface and interfaces, the total conductivity is given by a sum of conductivities of all the subbands and two spin-channels. For each subband and each spin-channel the scattering rate due to the impurities, surface and interfaces is added up.
基金supported by the National Natural Science Foundation of China(Grant Nos.11074040,11504192,11674187,11604172,and 51403114)the Natural Science Foundation of Shandong Province,China(Grant Nos.ZR2012FZ006 and BS2014CL010)the China Postdoctoral Science Foundation(Grant Nos.2014M551868 and 2015M570570)
文摘A special Fe3O4nanoparticles–graphene（Fe3O4–GN） composite as a magnetic label was employed for biodetection using giant magnetoresistance（GMR） sensors with a Wheatstone bridge. The Fe3O4–GN composite exhibits a strong ferromagnetic behavior with the saturation magnetization MS of approximately 48 emu/g, coercivity HC of 200 Oe, and remanence Mr of 8.3 emu/g, leading to a large magnetic fringing field. However, the Fe3O4 nanoparticles do not aggregate together, which can be attributed to the pinning and separating effects of graphene sheet to the magnetic particles. The Fe3O4–GN composite is especially suitable for biodetection as a promising magnetic label since it combines two advantages of large fringing field and no aggregation. As a result, the concentration x dependence of voltage difference ｜？V｜ between detecting and reference sensors undergoes the relationship of ｜？V｜ = 240.5 lgx ＋ 515.2 with an ultralow detection limit of 10 ng/mL（very close to the calculated limit of 7 ng/mL） and a wide detection range of 4 orders.
基金Funded by the National Natural Science Foundation of Guangxi and Guangxi Key Laboratory of Information Materials Foundation (No.0575093&0710908-11-Z)
文摘Prx（Co40Ag60）100-x （x=0, 0.5, 1, 1.5, 2, 3） granular films have been prepared by DC magneto controlled sputtering method. The XRD data indicated that Pr element favors the （111） plane preferential orientation. Magnetic measurements indicate that the average size of magnetic particles decreases as Pr content increases. For relatively low addition of Pr to CoAg granular films, Pr element can enhance GMR value and a peak value of about -14.3% is obtained at x=1.
文摘The structure and microfabrication,the detecting theory and the way of biomolecular recognition device based on giant magnetoresistance(GMR) effect are introduced,also the signal detecting and processing instrumentation are presented. Here the GMR biosensor was fabricated with magnetic tunnel junction(MJT) material.The biomolecular recognition device contains an array of MJT sensors,single MJT sensor size is 10μm×20μm,tunneling magnetoresistance ratio(TMR) at room temperature is 52.2%,the typical values of junction resistance-area product Rs is 2.6 kΩμm^2,detecting sensitivity of this system is about 8×10^(-4) A·m^(-1).Bioadaptation layer of this device was fabricated with PDMS the thickness of which is less than 100 nm.
文摘A phenomenological theoretical model for magnetic multilayer based on Boltzmann equation and Fuchs-Sondheimer theory is studied. An oscillatory transmission coefficient (Ts) is introduced into the boundary conditions to simulate the alternate ferromagnetic and anti-ferromagnetic coupling between the magnetic layers. The transmission coefficient has an oscillatory factor relating to the thickness of space layer. Other effects such as interface roughness on Ts are also taken into account. The numerical results for [Fe/Cr]n multilayer agree with the experimental data very well, both in the period and range of osciallation, which is leaded by the dependence of giant magnetoresistance(GMR) on layer thickness of space layer.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51125004,10974120,B13029 and JQ200901)the National Basic Research Program of China (Grant Nos. 2013CB922303and 2009CB929202)
文摘With the discovery of giant magnetoresistance(GMR),research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials and/or artificial structures,which has lead to the idea of spintronics.A brief introduction is given to GMR effects from scientific background to experimental observations and theoretical models.In addition,the mechanisms of various magnetoresistance beyond the GMR are reviewed,for instance,tunnelling magnetoresistance,colossal magnetoresistance,and magnetoresistance in ferromagnetic semiconductors,nanowires,organic spintronics and non-magnetic systems.
基金This work was supported by the Research Grant Council of Hong Kong(N_PolyU540/17)the Shenzhen Science and Technology Innovation Commission(JCYJ20180507183424383)the Hong Kong Polytechnic University(G-SB79 and G-YBPS).
文摘The atomic structure of quasi one-dimensional(1D) van der Waals materials can be regarded as the stacking of atomic chains to form thin flakes or nanoribbons, which substantially differentiates them from typical two-dimensional(2D) layered materials and 1D nanotube/nanowire array. Here we present our studies on quasi 1D gold selenide(AuSe) that possesses highly anisotropic crystal structure, excellent electrical conductivity, giant magnetoresistance, and unusual reentrant metallic behavior. The low inplane symmetry of AuSe gives rise to its high anisotropy of vibrational behavior. In contrast, quasi 1D AuSe exhibits high in-plane electrical conductivity along the directions of both atomic chains and perpendicular one, which can be understood as a result of strong interchain interaction. We found that AuSe exhibits a near quadratic nonsaturating giant magnetoresistance of 1841% with the magnetic field perpendicular to its in-plane. We also observe unusual reentrant metallic behavior, which is caused by the carrier mismatch in the multiband transport. Our works help to establish fundamental understandings on quasi 1D van der Waals semimetallic AuSe and identify it as a new candidate for exploring giant magnetoresistance and compensated semimetals.
基金the National Natural Science Foundation of China(Grant Nos.11804062,and 11804082)the National Key Research and Development Program(Grant No.2018YFB0407600)。
文摘Recent studies on the electrical switching of tetragonal antiferromagnet(AFM)via Neél spin-orbit torque have paved the way for the economic use of antiferromagnetic materials.The most difficult obstacle that presently limits the application of antiferromagnetic materials in spintronics,especially in memory storage applications,could be the small and fragile magnetoresistance(MR)in the AFM-based nanostructure.In this study,we investigated the spin transports in Mn2Au-based tunnel junctions based on the first-principle scattering theory.Giant MRs more than 1000%are predicted in some Fe/MgO/Ag/Mn2Au/Ta junctions that are about the same order as that in an MgO-based ferromagnetic tunnel junction with same barrier thickness.The interplay of the spin filtering effect,the quantum well resonant states,and the interfacial resonant states could be responsible for the unusual giant and robust MRs observed in these Mn2Au-based junctions.
基金supported by the National Natural Science Foundation of China.
文摘Magnetoresistanoe in the temperature region from 300 K to liquid helium temperature has been measured on good (100) oriented La2/3Ca1/3MnO2 thin films prepared by d.c. magnetron sputtering on ZrO2 (100) substrates. It is found that there appears a resistance peak at about TP = 72K at zero magnetic field, and this peak moves to higher temperature with increasing field H, and R decreases simultaneously. However, the magnetoresistance ratio MR = 5R /R (H) = (Ro~ RH) /RH has a different temperature dependence. There are also MR peaks, but the temperature of maximum MR is at about 25 K which does not change with changing external magnetic field. The heat treatment (annealed at 700C in 105’Pa O2 for 30min) will make R reduce dramatically and has an effect on the temperature dependence of R and its MR.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11547249,51501102,and 11647157)the Science Foundation for Excellent Youth Doctors of Three Gorges University,China(Grant No.KJ2014B076)
文摘The transport property of electrons tunneling through arrays of magnetic and electric barriers is studied in silicene. In the tunneling transmission spectrum, the spin-valley-dependent filtered states can be achieved in an incident energy range which can be controlled by the electric gate voltage. For the parallel magnetization configuration, the transmission is asymmetric with respect to the incident angle θ, and electrons with a very large negative incident angle can always transmit in propagating modes for one of the spin-valley filtered states under a certain electromagnetic condition. But for the antiparallel configuration, the transmission is symmetric about θ and there is no such transmission channel. The difference of the transmission between the two configurations leads to a giant tunneling magnetoresistance （TMR） effect. The TMR can reach to 100% in a certain Fermi energy interval around the electrostatic potential. This energy interval can be adjusted significantly by the magnetic field and/or electric gate voltage. The results obtained may be useful for future valleytronic and spintronic applications, as well as magnetoresistance device based on silicene.
基金This work was supported by the National Natural Science Foundation of China under grant No.50071039,50271046supported by the United Academy of Education Ministry,Tianjin University and Nankai University.
文摘Granular CoxCu1-x alloy films were prepared by electrodeposition at room temperature directly onto semiconducting Si substrate. X-ray diffraction (XRD) revealed that the as-deposited films formed single phase metastable fcc alloy structure. The fcc lattice parameter α was found to decrease linearly with increasing Co concentration x in the studied range. The giant magnetoresistance (GMR) of the films was improved after annealing. Pure Co fcc diffraction peaks were observed in the diffractogram of the annealed sample, indicating phase separation occurred upon annealing. The optimal annealing temperature was 450℃. The maximum of magnetoresistance (MR) ratio 8.21% was obtained for the Co20Cu80 thin film after annealing at 450℃ for 1 h. The saturation field decreased upon annealing in the MR curves of Co20Cu80 film.
文摘Thickness effects of thin La0.7Sr0.3MnO3 （LSMO） films on （LaAlOa）0.3（Sr2AlTaO6）0.7 substrates were examined by a slow positron beam technique. Doppler-broadening line shape parameter S was measured as a function of thickness and differnt annealing conditions. Results reveal there could be more than one mechanism to induce vacancy-like defects. It was found that strain-induced defects mainly influence the S value of the in situ oxygenambience annealing LSMO thin films and the strain could vanish still faster along with the increase of thickness, and the oxygen-deficient induced defects mainly affect the S value of post-annealing LSMO films.
基金Supported by National Natural Science Foundation of China!(No.194 7710 5)
文摘The quantum phenomenological model has been proposed to investigate the magnetic property of nanometer magnetic granular film in an applied magnetic field.The magnetoresistance of the granular films with two distinct magnetic phases has been calculated by using Born approximation.The results show that the average scattering cross section of the magnetic cluster decreases with the increasing number n of the atom.The origin of the giant magnetoresistance comes from the spin dependent scattering between conduction electrons and magnetic granules and the field dependence of magnetoresistance and the quadratic relation of magnetoresistance on the rate of magnetic moment are in good agreement with the experiments reported.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11174295,51001094,91222109,51171177,and 50701042)the National Key Basic Research of China (Grant No. 2011CBA00111)
文摘Our recent research on the Mn-based antiperovskite functional materials AXMn3 （A： metal or semiconducting elements; X： C or N） is outlined. Antiperovskite carbides （e.g., AlCMn3） show large magnetocaloric effect comparable to those of typical magnetic refrigerant materials. Enhanced giant magnetoresistance up to 70% at 50 kOe （1 Oe=79.5775 A.m-1） over a wide temperature span was obtained in Ga1-xZnxCMn3 and GaCMn3 xNix. In Cu0.3Sn0.5NMn3.2, negative thermal expansion （NTE） was achieved in a wide temperature region covering room temperature （α = -6.8 ppm/K, 150 K-40 K）. Neutron pair distribution function analysis suggests the Cu/Sn-Mn bond fluctuation is the driving force for the NTE in Cu1- xSnxNMn3. In CuN1- xCxMn3 and CuNMn3 yCoy, the temperature coefficient of resistivity （TCR） decreases monotonically from positive to negative as Co or C content increases. TCR is extremely low when the composition approaches the critical points. For example, TCR is - 1.29 ppm/K between 240 K and 320 K in CuN0.95C0 05Mn3, which is one twentieth of that in the typical low-TCR materials （- 25 ppm/K）. By studying the critical scaling behavior and X deficiency effect, some clues of localized-electron magnetism have been found against the background of electronic itinerant magnetism.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10574082 and 10474056, and the Natural Science Foundation of Shandong Province under Grant No Z2005A01.
文摘Considering the special carriers in organic semiconductors, the spin polarized current under electric field in a ferromagnetic/organic semiconductor system is theoretically studied. Based on the spin-diffusion theory, the current spin polarization under the electric field is obtained. It is found that electric field can enhance the current spin polarization.
