Magnon-magnon coupling in synthetic antiferromagnets advances it as hybrid magnonic systems to explore the quantum information technologies.To induce magnon-magnon coupling,the parity symmetry between two magnetizatio...Magnon-magnon coupling in synthetic antiferromagnets advances it as hybrid magnonic systems to explore the quantum information technologies.To induce magnon-magnon coupling,the parity symmetry between two magnetization needs to be broken.Here we experimentally demonstrate a convenient method to break the parity symmetry by the asymmetric structure.We successfully introduce a magnon-magnon coupling in Ir-based synthetic antiferromagnets CoFeB(10 nm)/Ir(t_(Ir)=0.6 nm,1.2 nm)/CoFeB(13 nm).Remarkably,we find that the weakly uniaxial anisotropy field(-20 Oe)makes the magnon-magnon coupling anisotropic.The coupling strength presented by a characteristic anticrossing gap varies in the range between 0.54 GHz and 0.90 GHz for t_(Ir)=0.6 nm,and between 0.09 GHz and 1.4 GHz for t_(Ir)=1.2 nm.Our results demonstrate a feasible way to induce magnon-magnon coupling by an asymmetric structure and tune the coupling strength by varying the direction of in-plane magnetic field.The magnon-magnon coupling in this highly tunable material system could open exciting perspectives for exploring quantum-mechanical coupling phenomena.展开更多
Amorphous MnxGe1-x：H ferromagnetic semiconductor films prepared in mixed Ar with 20% H2 by magnetron co- sputtering show global ferromagnetism with positive coercivity at low temperatures. With increasing temperature...Amorphous MnxGe1-x：H ferromagnetic semiconductor films prepared in mixed Ar with 20% H2 by magnetron co- sputtering show global ferromagnetism with positive coercivity at low temperatures. With increasing temperature, the coercivity of MnxGe1-x：H films first changes from positive to negative, and then back to positive again, which was not found in the corresponding MnxGe1-x and other ferromagnetic semiconductors before. For Mn0.4Ge0.6：H film, the inverted Hall loop is also observed at 30 K, which is consistent with the negative coercivity. The negative coercivity is explained by the antiferromagnetic exchange coupling between the H-rich ferromagnetic regions separated by the H-poor non-ferromagnetic spacers. Hydrogenation is a useful method to tune the magnetic properties of MnxGe1-x films for the application in spintronics.展开更多
Two novel coordination compounds formulated as [Co2（EY）2（L1）]·2C2H5OH（1） and [Mn2（EY）2（L1）]·2C2H5OH（2）（EY = Eosin Y dianion, L1 = 4,4＇-bipyridine） based on Eosin Y dye ligand have been prepare...Two novel coordination compounds formulated as [Co2（EY）2（L1）]·2C2H5OH（1） and [Mn2（EY）2（L1）]·2C2H5OH（2）（EY = Eosin Y dianion, L1 = 4,4＇-bipyridine） based on Eosin Y dye ligand have been prepared by solvothermal reactions and structurally characterized. Single-crystal X-ray diffraction studies reveal that compounds 1 and 2 are isostructural. They show weak antiferromagnetic coupling between the adjacent Co^Ⅱ and Mn^Ⅱ ions, respectively.展开更多
The Fe/Mo multilayers were prepared by electron beam evaporation, the micro structure and magnetic properties of the multilayers were studied by X-ray diffraction, vibrating-sample magnetometer (VSM) et al. The experi...The Fe/Mo multilayers were prepared by electron beam evaporation, the micro structure and magnetic properties of the multilayers were studied by X-ray diffraction, vibrating-sample magnetometer (VSM) et al. The experimental results revealed that the Fe/Mo multilayers in our experimental conditions behaved magnetoresistance effect with a sharp peak on magnetoresistance (MR) ratio curve, and magnetoresistance is easily saturated at low applied magnetic fields. For [Fe(1.5nm)/Mo(1.0nm)]4,2 multilayers, MR ratio could arrive to 0.1%. The antiferromagnetic interlayer coupling could be observed in some films at room temperature. The strength of the antiferromagnetic interlayer coupling J in the films is low because of the low saturation field Hs. The relationship between magnetic properties and micro structure was also discussed in this paper.展开更多
The study on temperature dependence of exchange bias field and coercivity is crucial to solving the writing/reading dilemma in magnetic recording.Motivated by recent experimental findings,a complete switch between exc...The study on temperature dependence of exchange bias field and coercivity is crucial to solving the writing/reading dilemma in magnetic recording.Motivated by recent experimental findings,a complete switch between exchange bias field and coercivity with temperature is proposed,and the performance,characterized by average switching temperature(T_(S))and switching temperature width(T_(W)),controlled by antiferromagnetic anisotropy(KAF)and exchange coupling(J_(AF))constants is studied based on a MonteCarlo simulation.The results show that a linear relationship between T_(S)and KAFis established when KAFis above a critical value,while T_(S)is weakly influenced by J_(AF).On the contrary,T_(W)is insensitive to KAF,while strongly depends on J_(AF).Besides overcoming thermal energy,the increase of KAFfor a small J_(AF)guarantees the completely frozen states in the antiferromagnetic layers during magnetizing at higher temperature,below which the exchange bias field exists with a negligible coercivity.Otherwise,for a large J_(AF),the uncompensated antiferromagnetic magnetization behavior during the ferromagnetic magnetization reversal becomes complicated,and the switching process in the low temperature range depends on the irreversibility of uncompensated antiferromagnetic magnetization reversal during magnetizing,while in the high temperature range mainly influenced by the field-cooling process,resulting in a large T_(W).This work provides an opportunity to control/optimize the performance of the temperatureinduced switch between unidirectional and uniaxial symmetries through precisely tuning KAFand/or J_(AF)to meet different application demands in the next generation information technology.展开更多
A new cobalt vanadate compound 1 [CoII(H2O)2V2VO6] has been hydrothermally synthesized and characterized by the elemental analyses and the single crystal X-ray diffraction analysis. Compound 1 crystallizes in the orth...A new cobalt vanadate compound 1 [CoII(H2O)2V2VO6] has been hydrothermally synthesized and characterized by the elemental analyses and the single crystal X-ray diffraction analysis. Compound 1 crystallizes in the orthorhombic system, space group Pmna, with a=0.55646, b=1.06900, c=1.18452 nm, and Z=4. The magnetic susceptibility of the cobalt vanadate has been measured and indicates possible antiferromagnetic coupling between adjacent cobalt (II) (0.54320.5697 nm) through bond or space.展开更多
基金Supported by the National Natural Science Foundation of China (Grant Nos.51871235,51671212,52031014,51771198,and51801212)the National Key Research and Development Program of China (Grant Nos.2016YFA0300701,2017YFB0702702,and2017YA0206302)+2 种基金the Key Research Program of Frontier Sciences,CAS (Grant Nos.QYZDJ-SSW-JSC023,KJZD-SW-M01ZDYZ2012-2)support from the Natural Science Foundation for Distinguished Young Scholars of Hebei Province of China (S&T Program of Hebei,Grant No.A2019205310)。
文摘Magnon-magnon coupling in synthetic antiferromagnets advances it as hybrid magnonic systems to explore the quantum information technologies.To induce magnon-magnon coupling,the parity symmetry between two magnetization needs to be broken.Here we experimentally demonstrate a convenient method to break the parity symmetry by the asymmetric structure.We successfully introduce a magnon-magnon coupling in Ir-based synthetic antiferromagnets CoFeB(10 nm)/Ir(t_(Ir)=0.6 nm,1.2 nm)/CoFeB(13 nm).Remarkably,we find that the weakly uniaxial anisotropy field(-20 Oe)makes the magnon-magnon coupling anisotropic.The coupling strength presented by a characteristic anticrossing gap varies in the range between 0.54 GHz and 0.90 GHz for t_(Ir)=0.6 nm,and between 0.09 GHz and 1.4 GHz for t_(Ir)=1.2 nm.Our results demonstrate a feasible way to induce magnon-magnon coupling by an asymmetric structure and tune the coupling strength by varying the direction of in-plane magnetic field.The magnon-magnon coupling in this highly tunable material system could open exciting perspectives for exploring quantum-mechanical coupling phenomena.
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 11204164)the National Natural Science Foundation of China (Grant No. 11174184)+1 种基金the National Basic Research Program of China (Grants Nos. 2013CB922303 and 2009CB929202)the National Funds for Distinguished Young Scholars of China (Grant No. 51125004)
文摘Amorphous MnxGe1-x：H ferromagnetic semiconductor films prepared in mixed Ar with 20% H2 by magnetron co- sputtering show global ferromagnetism with positive coercivity at low temperatures. With increasing temperature, the coercivity of MnxGe1-x：H films first changes from positive to negative, and then back to positive again, which was not found in the corresponding MnxGe1-x and other ferromagnetic semiconductors before. For Mn0.4Ge0.6：H film, the inverted Hall loop is also observed at 30 K, which is consistent with the negative coercivity. The negative coercivity is explained by the antiferromagnetic exchange coupling between the H-rich ferromagnetic regions separated by the H-poor non-ferromagnetic spacers. Hydrogenation is a useful method to tune the magnetic properties of MnxGe1-x films for the application in spintronics.
基金supported by the National Natural Science Foundation of China(21503230 and 21571175)State Key Laboratory of Structural Chemistry,Fujian Institute of Research on the Structure of Matter,Chinese Academy of Sciences
文摘Two novel coordination compounds formulated as [Co2（EY）2（L1）]·2C2H5OH（1） and [Mn2（EY）2（L1）]·2C2H5OH（2）（EY = Eosin Y dianion, L1 = 4,4＇-bipyridine） based on Eosin Y dye ligand have been prepared by solvothermal reactions and structurally characterized. Single-crystal X-ray diffraction studies reveal that compounds 1 and 2 are isostructural. They show weak antiferromagnetic coupling between the adjacent Co^Ⅱ and Mn^Ⅱ ions, respectively.
文摘The Fe/Mo multilayers were prepared by electron beam evaporation, the micro structure and magnetic properties of the multilayers were studied by X-ray diffraction, vibrating-sample magnetometer (VSM) et al. The experimental results revealed that the Fe/Mo multilayers in our experimental conditions behaved magnetoresistance effect with a sharp peak on magnetoresistance (MR) ratio curve, and magnetoresistance is easily saturated at low applied magnetic fields. For [Fe(1.5nm)/Mo(1.0nm)]4,2 multilayers, MR ratio could arrive to 0.1%. The antiferromagnetic interlayer coupling could be observed in some films at room temperature. The strength of the antiferromagnetic interlayer coupling J in the films is low because of the low saturation field Hs. The relationship between magnetic properties and micro structure was also discussed in this paper.
基金financially supported by the National Natural Science Foundation of China(No.11774045)the Joint Research Fund Liaoning-Shenyang National Laboratory for Materials Science(No.20180510008)。
文摘The study on temperature dependence of exchange bias field and coercivity is crucial to solving the writing/reading dilemma in magnetic recording.Motivated by recent experimental findings,a complete switch between exchange bias field and coercivity with temperature is proposed,and the performance,characterized by average switching temperature(T_(S))and switching temperature width(T_(W)),controlled by antiferromagnetic anisotropy(KAF)and exchange coupling(J_(AF))constants is studied based on a MonteCarlo simulation.The results show that a linear relationship between T_(S)and KAFis established when KAFis above a critical value,while T_(S)is weakly influenced by J_(AF).On the contrary,T_(W)is insensitive to KAF,while strongly depends on J_(AF).Besides overcoming thermal energy,the increase of KAFfor a small J_(AF)guarantees the completely frozen states in the antiferromagnetic layers during magnetizing at higher temperature,below which the exchange bias field exists with a negligible coercivity.Otherwise,for a large J_(AF),the uncompensated antiferromagnetic magnetization behavior during the ferromagnetic magnetization reversal becomes complicated,and the switching process in the low temperature range depends on the irreversibility of uncompensated antiferromagnetic magnetization reversal during magnetizing,while in the high temperature range mainly influenced by the field-cooling process,resulting in a large T_(W).This work provides an opportunity to control/optimize the performance of the temperatureinduced switch between unidirectional and uniaxial symmetries through precisely tuning KAFand/or J_(AF)to meet different application demands in the next generation information technology.
基金Project supported by the National Natural Science Foundation of China (No. 20274006).
文摘A new cobalt vanadate compound 1 [CoII(H2O)2V2VO6] has been hydrothermally synthesized and characterized by the elemental analyses and the single crystal X-ray diffraction analysis. Compound 1 crystallizes in the orthorhombic system, space group Pmna, with a=0.55646, b=1.06900, c=1.18452 nm, and Z=4. The magnetic susceptibility of the cobalt vanadate has been measured and indicates possible antiferromagnetic coupling between adjacent cobalt (II) (0.54320.5697 nm) through bond or space.
