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Chinese Physics B 2012年第7期21卷 5-10页

作者：刘郝亮何为杜海峰房亚鹏吴琼张向群杨海涛成昭华 State Key Laboratory of Magnetism and Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China

The magnetic anisotropy and magnetization reversal of single crystal Fe films with thickness of 45 monolayer （ML） grown on Si（111） have been investigated by ferromagnetic resonance （FMR） and vibrating sample magnetometer （VSM）. Owing to the significant modification of the energy surface in remanent state by slight misorientation from （111） plane and a uniaxial magnetic anisotropy, the azimuthal angular dependence of in-plane resonance field shows a six-fold symmetry with a weak uniaxial contribution, while the remanence of hysteresis loops displays a two-fold one. The competition between the first and second magnetoerystalline anisotropies may result in the switching of in-plane easy axis of the system. Combining the FMR and VSM measurements, the magnetization reversal mechanism has also been determined.

关键词： magnetic anisotropy magnetization reversal ultrathin film

magnetic anisotropy in 5d transition metal-porphyrin molecules

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Chinese Physics B 2021年第4期30卷 508-511页

作者： Yan-Wen Zhang Gui-Xian Ge Hai-Bin Sun Jue-Ming Yang Hong-Xia Yan Long Zhou Jian-Guo Wan Guang-Hou Wang Key Laboratory of Ecophysics and Department of Physics College of ScienceShihezi UniversityShihezi832003China Key Laboratory of Advanced Micro/Nano Functional Materials Department of Physics and Electronic EngineeringXinyang Normal UniversityXinyang464000China National Laboratory of Solid State Microstructures and Department of Physics Nanjing UniversityNanjing210093China

Single molecule magnets(SMMs) with large magnetic anisotropy energy(MAE) have great potential applications in magnetic *** the first-principles calculations,we investigate the MAE of 5 d transition metal-porphyrin-based SMMs by using the PBE and PBE+U with different U values,*** results indicate that W-P,Re-P,Os-P,and Ir-P possess the considerably large MAE among 5 d TM-P ***,the MAE of 5 d TM-P can be facilely manipulated by tensile *** reduction of the absolute value of MAE for Ir-P molecule caused by tensile strain makes it easier to implement the writing *** decreasing of the occupation number of minority-spin channels of Ir-d_(x^(2)-y^(2)) orbital leads the MAE to decrease when the tensile strain increases.

关键词： the first principle calculations single molecule magnets magnetic anisotropy

magnetic anisotropy,exchange coupling and Dzyaloshinskii–Moriya interaction of two-dimensional magnets

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Frontiers of physics 2023年第1期18卷 29-45页

作者： Qirui Cui Liming Wang Yingmei Zhu Jinghua Liang Hongxin Yang Ningbo Institute of Materials Technology and Engineering Chinese Academy of SciencesNingbo 315201China School of Physics Nanjing UniversityNanjing 210093China Center of Materials Science and Optoeledctronics Engineering University of Chinese Academy of SciencesBeijing 100049China

The two-dimensional(2D)magnets provide novel opportunities for understanding magnetism and investigating spin related phenomena in several atomic *** features of 2D magnets,such as critical temperatures,magnetoelectric/magneto-optic responses,and spin configurations,depend on the basic magnetic terms that describe various spins interactions and cooperatively determine the spin Hamiltonian of studied *** this review,we present a comprehensive survey of three types of basic terms,including magnetic anisotropy that is intimately related with longrange magnetic order,exchange coupling that normally dominates the spin interactions,and Dzyaloshinskii–Moriya interaction(DMI)that favors the noncollinear spin configurations,from the theoretical *** introduce not only the physical features and origin of these crucial terms in 2D magnets but also many correlated phenomena,which may lead to the advance of 2D spintronics.

关键词： magnetic anisotropy exchange coupling Dzyaloshinskii-Moriya interaction two-dimensional magnets

Tuning magnetic anisotropy by interfacial engineering in La2/3Sr1/3Co1-xMnxO2.5+δ/La2/3Sr1/3MnO3/La2/3Sr1/3Co1-xMnxO2.5+δ trilayers

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Chinese Physics B 2020年第9期29卷 498-505页

作者： Hai-Lin Huang Liang Zhu Hui Zhang Jin-E Zhang Fu-Rong Han Jing-Hua Song Xiaobing Chen Yuan-Sha Chen( Jian-Wang Cai Xue-Dong Bai Feng-Xia Hu Bao-Gen Shen Ji-Rong Sun Beijing National Laboratory for Condensed Matter Physics&Institute of Physics Chinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China Songshan Lake Materials Laboratory Dongguan 523808China

Grouping different oxide materials with coupled charge, spin, and orbital degrees of freedom together to form heterostructures provides a rich playground to explore the emergent interfacial phenomena. The perovskite/brownmillerite heterostructure is particularly interesting since symmetry mismatch may produce considerable interface reconstruction and unexpected physical effects. Here, we systemically study the magnetic anisotropy of tensely strained La2/3Sr1/3Co1-xMnxO2.5+δ/La2/3Sr1/3MnO3/La2/3Sr1/3Co1-xMnxO2.5+δ trilayers with interface structures changing from perovskite/brownmillerite type to perovskite/perovskite type. Without Mn doping, the initial La2/3Sr1/3CoO2.5+δ/La2/3Sr1/3MnO3/La2/3Sr1/3CoO2.5+δ trilayer with perovskite/brownmillerite interface type exhibits perpendicular magnetic anisotropy and the maximal anisotropy constant is 3.385×106 erg/cm3, which is more than one orders of magnitude larger than that of same strained LSMO film. By increasing the Mn doping concentration, the anisotropy constant displays monotonic reduction and even changes from perpendicular magnetic anisotropy to in-plane magnetic anisotropy, which is possible because of the reduced CoO4 tetrahedra concentration in the La2/3Sr1/3Co1-xMnxO2.5+δ layers near the interface. Based on the analysis of the x-ray linear dichroism, the orbital reconstruction of Mn ions occurs at the interface of the trilayers and thus results in the controllable magnetic anisotropy.

关键词： perovskite/brownmillerite heterostructure magnetic anisotropy orbital reconstruction

Thickness dependent manipulation of uniaxial magnetic anisotropy in Fe-thin films by oblique deposition

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Chinese Physics B 2018年第9期27卷 577-584页

作者： Qeemat Gul Wei He Yan Li Rui Sun Na Li Xu Yang Yang Li Zi-Zhao Gong ZongKai Xie Xiang-Qun Zhang Zhao-Hua Cheng State Key Laboratory of Magnetism and Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China

The uniaxial magnetic anisotropy of obliquely deposited Fe（001）/Pd film on MgO（001） substrate is investigated as a function of deposition angle and film thickness. The values of incidence angle of Fe flux relative to surface normal of the substrate are 0°, 45°, 55°, and 70°, respectively. In-situ low energy electron diffraction is employed to investigate the surface structures of the samples. The Fe film thicknesses are determined to be 50 ML, 45 ML, 32 ML, and 24 ML（1 ML = 0.14 nm） by performing x-ray reflectivity on the grown samples, respectively. The normalized remanent magnetic saturation ratio and coercivity are obtained by the longitudinal surface magneto-optical Kerr effect. Here, the magnetic anisotropy constants are quantitatively determined by fitting the anisotropic magnetoresistance curves under different *** measurements show four-fold cubic anisotropy in a large Fe film thickness（50 ML） sample, but highly in-plane uniaxial magnetic anisotropies in thin films（24 ML and 32 ML） samples. In the obliquely deposited Fe films, the coercive fields and the uniaxial magnetic anisotropies（UMAs） increase as the deposition angle becomes more and more tilted. In addition, the UMA decreases with the increase of the Fe film thickness. Our work provides the possibility of manipulating uniaxial magnetic anisotropy, and paves the way to inducing UMA by oblique deposition with smaller film thickness.

关键词： iron thin films oblique deposition magnetic anisotropy magnetoresistance

Exchange-coupling-induced fourfold magnetic anisotropy in CoFeB/FeRh bilayer grown on SrTiO_(3)(001)

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Chinese Physics B 2022年第8期31卷 605-611页

作者： Qingrong Shao Jing Meng Xiaoyan Zhu Yali Xie Wenjuan Cheng Dongmei Jiang Yang Xu Tian Shang Qingfeng Zhan Key Laboratory of Polar Materials and Devices(MOE) School of Physics and Electronic ScienceEast China Normal UniversityShanghai 200241China Key Laboratory of magnetic Materials and Devices Ningbo Institute of Material Technology and EngineeringChinese Academy of SciencesNingbo 315201China

Exchange coupling across the interface between a ferromagnetic(FM)layer and an antiferromagnetic(AFM)or another FM layer may induce a unidirectional magnetic anisotropy and/or a uniaxial magnetic anisotropy,which has been extensively studied due to the important application in magnetic materials and *** this work,we observed a fourfold magnetic anisotropy in amorphous Co Fe B layer when exchange coupling to an adjacent Fe Rh layer which is epitaxially grown on an SrTiO_(3)(001)*** the temperature rises from 300 K to 400 K,Fe Rh film undergoes a phase transition from AFM to FM phase,the induced fourfold magnetic anisotropy in the Co Fe B layer switches the orientation from the Fe Rhto Fe Rhdirections and the strength is obviously *** addition,the effective magnetic damping as well as the two-magnon scattering of the Co Fe B/Fe Rh bilayer also remarkably increase with the occurrence of magnetic phase transition of Fe *** exchange bias is observed in the bilayer even when Fe Rh is in the nominal AFM state,which is probably because the residual FM Fe Rh moments located at the interface can well separate the exchange coupling between the below pinned Fe Rh moments and the Co Fe B moments.

关键词： magnetic anisotropy phase transition CoFeB/FeRh exchange coupling

Bismuth doping enhanced tunability of strain-controlled magnetic anisotropy in epitaxial Y_(3)Fe_(5)O_(12)(111) films

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Chinese Physics B 2023年第2期32卷 27-33页

作者：贾云鹏梁正国潘昊霖王庆吕崎鸣严轶非金锋侯达之王凌飞吴文彬 Hefei National Research Center for Physical Sciences at the Microscale University of Science and Technology of ChinaHefei 230026China Department of Physics University of Science and Technology of ChinaHefei 230026China Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field LaboratoryHFIPSAnhuiChinese Academy of SciencesHefei 230031China

Y_(3)Fe_(5)O_(12)(YIG) and Bi Y_(3)Fe_(5)O_(12)(Bi:YIG) films were epitaxially grown on a series of(111)-oriented garnet substrates using pulsed laser deposition. Structural and ferromagnetic resonance characterizations demonstrated the high epitaxial quality, extremely low magnetic loss and coherent strain state in these films. Using these epitaxial films as model systems, we systematically investigated the evolution of magnetic anisotropy(MA) with epitaxial strain and chemical doping. For both the YIG and Bi:YIG films, the compressive strain tends to align the magnetic moment in the film plane while the tensile strain can compete with the demagnetization effect and stabilize perpendicular MA. We found that the strain-induced lattice elongation/compression along the out-of-plane [111] axis is the key parameter that determines the MA. More importantly, the strain-induced tunability of MA can be enhanced significantly by Bi doping;meanwhile, the ultralow damping feature persists. We clarified that the cooperation between strain and chemical doping could realize an effective control of MA in garnet-type ferrites, which is essential for spintronic applications.

关键词： yttrium iron garnet strain engineering doping magnetic anisotropy

Manipulating magnetic anisotropy and ultrafast spin dynamics of magnetic nanostructures

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Chinese Physics B 2015年第7期24卷 3-22页

作者：成昭华何为张向群孙达力杜海峰吴琼叶军房亚鹏刘郝亮 State Key Laboratory of Magnetism Institute of PhysicsChinese Academy of Sciences

We present our extensive research into magnetic anisotropy. We tuned the terrace width of Si（111） substrate by a novel method： varying the direction of heating current and consequently manipulating the magnetic anisotropy of magnetic structures on the stepped substrate by decorating its atomic steps. Laser-induced ultrafast demagnetization of a Co FeB/MgO/CoFeB magnetic tunneling junction was explored by the time-resolved magneto-optical Kerr effect（TRMOKE） for both the parallel state（P state） and the antiparallel state（AP state） of the magnetizations between two magnetic layers. It was observed that the demagnetization time is shorter and the magnitude of demagnetization is larger in the AP state than those in the P state. These behaviors are attributed to the ultrafast spin transfer between two CoFeB layers via the tunneling of hot electrons through the MgO barrier. Our observation indicates that ultrafast demagnetization can be engineered by the hot electron tunneling current. This opens the door to manipulate the ultrafast spin current in magnetic tunneling junctions. Furthermore, an all-optical TR-MOKE technique provides the flexibility for exploring the nonlinear magnetization dynamics in ferromagnetic materials, especially with metallic materials.

关键词： magnetic anisotropy ultrafast spin dynamics magnetic nanostructures

Structures and magnetic anisotropy of β-Mn_2V_2O_7 crystals synthesized by the molten salt method

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Chinese Physics B 2009年第11期18卷 5055-5060页

作者：周传仓刘发民丁芃 Department of Physics School of Physics and Nuclear Energy EngineeringBeijing University of Aeronautics and Astronautics

β-Mn2V2O7 crystals with strip shape are successfully prepared by the molten salt method in a closed crucible, and are characterized by x-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, selected area of electron diffraction （SAED） and high-resolution transmission electron microscopy （HRTEM）. The results indicate that the sample is of the β-Mn2V2O7 crystal with monoclinic symmetry, level natural cleavage facets and directional growth. magnetic properties are measured by vibration sample magnetometry （VSM） at room temperature, and the magnetic hysteresis loop indicates that the β-Mn2V2O7 has anti-ferromagnetic properties with low coercive force and remnant magnetization. The magnetic measurement results in different directions exhibit that the β-Mn2V2O7 has magnetic anisotropy, which is due to the fact that the magnetic interaction energy of the β-Mn2V2O7 is lowest only when the electron configuration is in a certain direction.

关键词： β-Mn2V2O7 molten salt synthesis magnetic anisotropy

Increase of chiral sensing ability in host-guest chemistry by magnetic anisotropy

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Science China Chemistry 2024年第8期67卷 2775-2782页

作者： Jia-Liang Chen Bin Li Feng Yang Tiesheng Shi Xun-Cheng Su State Key Laboratory of Elemento-organic Chemistry Tianjin Key Laboratory of Biosensing and Molecular RecognitionCollege of ChemistryNankai UniversityTianjin 300071China College of Chemistry Chemical Engineering and Materials ScienceZaozhuang UniversityZaozhuang 277160China

Enantiomeric molecules generally play distinct functions in chemistry,biology,and *** physical and chemical properties of chiral analytes lay difficulty in discrimination and quantification of the *** report herein an efficient approach of increasing the chiral sensing ability ofβ-cyclodextrin(β-CD),a widely used host molecule,in the hostguest chemistry by magnetic anisotropy.A rigid and chiral lanthanide binding tag was attached to theβ-CD to amplify the changes of nuclear magnetic resonance(NMR)signals in the host-guest recognition *** installation of the paramagnetic lanthanide ion inβ-CD greatly enhances the enantiomeric discrimination up to 30-fold in comparison with the diamagneticβ-CD *** addition,the magnitude of the paramagnetic effects is tunable according to the diverse range of paramagnetic strength of the lanthanide *** reported method significantly increases the chiral sensing ability ofβ-CD,which can be applied to other host *** transferred paramagnetic effects,pseudocontact shifts(PCSs)and paramagnetic relaxation enhancements(PREs),from the host to the guest molecules,are valuable structural restraints to determine the absolute stereochemistry of the chiral *** strategy does not need modification of the analytes and is complementary to the reported analytical methods that rely on the functionalization of the chiral analytes.

关键词： chiral recognition nuclear magnetic resonance host-guest chemistry magnetic anisotropy lanthanide ions