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ferrimagnetism induced by asymmetrical ferromagnetic next-nearest-neighbour exchange interactions in an antiferromagnetic spin-1/2 zigzag chain

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Chinese Physics B 2011年第9期20卷 408-414页

作者：王忠龙傅华华 Science College China Three Gorges University School of Physics Huazhong University of Science and Technology

The magnetic properties of an antiferromagnetic bond alternating spin-l/2 zigzag chain with asymmetrical ferro- magnetic next-nearest-neighbour exchange interactions at finite temperature are investigated by using the many-body Green＇s function theory. It is found that the ferrimagnetic ordering does not appear in the symmetrical next-nearest- neighbour coupling case, and takes place only for the asymmetrical next-nearest-neighbour case at finite temperature rather than the ground state. Furthermore, as the asymmetry degree of the next-nearest-neighbour exchange inter- actions increases, the ferrimagnetism becomes more and more dominant. It is shown that the elementary excitation spectra are responsible for the observed magnetic behaviour.

关键词： ferrimagnetism Green＇s function theory zigzag spin chain

Anomalous Hall effect in ferromagnetic LaCo_(2)As_(2) and ferrimagnetic NdCo_(2)As_(2)

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中国物理B:英文版 2023年第10期32卷 641-648页

作者：黄雨晴郑鹏宇刘瑞许锡童吴紫阳董超王俊峰殷志平贾爽 International Center for Quantum Materials School of PhysicsPeking UniversityBeijing 100081China Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory Xianhu Hydrogen ValleyFoshan 528200China Department of Physics and Center for Advanced Quantum Studies Beijing Normal UniversityBeijing 100875China Wuhan National High Magnetic Field Center and School of Physics Huazhong University of Science and TechnologyWuhan 430074China Kunshan Innovation Institute of Nanjing University Kunshan 215347China

We conducted a comparative study of the magnetic and transport properties of single-crystalline LaCo_(2)As_(2) and NdCo_(2)As_(2).LaCo_(2)As_(2) is a soft metallic ferromagnet which exhibits purely intrinsic anomalous Hall effect(AHE) due to Co-3d electrons. With Nd-4f electronic magnetism, ferrimagnetic NdCo_(2)As_(2) manifests pronounced sign reversal and multiple hysteresis loops in temperature-and field-dependent magnetization, Hall resistivity, and magnetoresistance, due to complicated magnetic structural changes. We reveal that the AHE for NdCo_(2)As_(2) is stemming from the Co sub-lattice and deduce its phase diagram which includes magnetic compensation and two meta-magnetic phase transitions. The sensitivity of the Hall effect on the details of the magnetic structures in ferrimagnetic NdCo_(2)As_(2) provides a unique opportunity to explore the magnetic interaction between 4f and 3d electrons and its impact on the electronic structure.

关键词： anomalous Hall effect ferrimagnetism magnetic compensation meta-magnetic transitions

Competition between Band Filling and Steric Effect in Ordered Double Perovskites Sr_(2-x)La_xMnMoO_6

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Journal of Rare Earths 2006年第6期24卷 679-684页

作者：田世哲赵军钗乔从德姬相玲姜炳政 State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun 130022China

The ordered double perovskites, Sr2-xLaxMnMoO6, were prepared by sol-gel reaction. Structural, magnetic, and electrical properties were investigated for a series of ordered double perovskites Sr2- x Lax MnMoO6 （0 ≤ x ≤ 1 ）. The compounds have a monoclinic structure （space group P21/n） and the cell volume expands monotonically with La doping. The Tc and the magnetic moment rise and the cusp-like transition temperature below which the magnetic frustration occurs shifts to high temperature as x increases. With La doping, electrical resistivity of Sr2-x LaxMnMoO6 decreases only at low doping levels （x ≤0.2）; while at high doping levels （0.8≤x ≤1）, electrical resistivity tends to increase greatly. The resuits suggest that the competition between band filling effect and steric effect coexists in the whole doping range, and the formation of ferrimagnetic interactions is not simply at the expense of antiferromagnetic interactions.

关键词： double perovskite band filling steric effect ferrimagnetism rare earths

Magnetizations and magneto-transport properties of Ni-doped PrFeO_3 thin films

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Chinese Physics B 2014年第4期23卷 608-615页

作者： Feroz A.Mir S.K.Sharma Ravi Kumar University Science Instrumentation Center University of Kashmir Instituto de Fisica Gleb Wataghin Universidade Estadual de Campinas (UNICAMP) CMSE National Institute of Technology

The present study reports the magnetizations and magneto-transport properties of PrFel_xNixO3 thin films grown by pulsed laser ablation technique on LaA103 snbstrates. From DC M/H plots of these films, weak ferromagnetism or ferrimagnetism behaviors are observed. With Ni substitution, reduction in saturation magnetization is also seen. With Ni doping, variations in saturation field （Hs）, coercive field （Hc）, Weiss temperature （0）, and effective magnetic moment （Pelf） are seen. A small change of magnetoresitance with application of higher field is observed. Various essential parameters like density of state （Nf） at Fermi level, Mott＇s characteristic temperature （To）, and activation energy （Ea） in the presence of and in the absence of magnetic field are calculated. The present observed magnetic properties are related to the change of Fe-O bond length （causing an overlap between the oxygen p orbital and iron d orbital） and the deviation of the Fe-O-Fe angle from 180~. Reduction of magnetic domain after Ni doping is also explored to explain the present observed magnetic behavior of the system. The influence of doping on various transport properties in these thin films indicates a distortion in the lattice structure and single particle band width, owing to stress-induced reduction in unit cell volume.

关键词： thin films magnetization ferromagnetism ferrimagnetism magneto-transport and distortion

Two-dimensional bipolar magnetic semiconductors with high Curie-temperature and electrically controllable spin polarization realized in exfoliated Cr(pyrazine)_(2) monolayers

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Science China Chemistry 2021年第12期64卷 2212-2217页

作者： Xiangyang Li Haifeng Lv Xiaofeng Liu Tong Jin Xiaojun Wu Xingxing Li Jinlong Yang Hefei National Laboratory of Physical Science at the Microscale Department of Chemical PhysicsSynergetic Innovation Center of Quantum Information&Quantum PhysicsUniversity of Science and Technology of ChinaHefei230026China Department of Chemistry Key Laboratory of Functional Inorganic Materials of Anhui ProvinceAnhui UniversityHefei230601China

Exploring two-dimensional(2D)magnetic semiconductors with room-temperature magnetic ordering and electrically controllable spin-polarization is a highly desirable but challenging task for nano-spintronics.Here,through first-principles calculations,we propose to realize such a material by exfoliating the recently synthesized organometallic layered crystal Li0.7[Cr(pyz)_(2)]Cl0.7·0.25(THF)(pyz=pyrazine,THF=tetrahydrofuran).The feasibility of exfoliation is confirmed by the rather low exfoliation energy of 0.27 J m^(−2),even smaller than that of graphite.In exfoliated Cr(pyz)_(2)monolayers,each pyrazine ring grabs one electron from the Cr atom to become a radical anion,and then a strong d-p direct-exchange magnetic interaction emerges between Cr cations and pyrazine radicals,resulting in room-temperature ferrimagnetism with a Curie temperature of 342 K.Moreover,the Cr(pyz)_(2)monolayer is revealed to be an intrinsic bipolar magnetic semiconductor where electrical doping can induce half-metallic conduction with controllable spin-polarization direction.

关键词： two-dimensional material ferrimagnetism bipolar magnetic semiconductor half metal first principles

Synthesis and Ferrimagnetic Behaviour of Mn Doped Rare Earth Iron Garnets

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Chemical Research in Chinese Universities 2012年第3期28卷 391-394页

作者： GUO Li YUAN Lin PENG Wen YUAN Hong-ming FENG Shou-hua State Key Laboratory of Inorganic Synthesis and Preparative Chemistry College of ChemistryJilin UniversityChangchun 130012R R.China

Rare earth iron garnets R3Fe5-xMnxO12（R=Pr, Nd, Sm, Eu） were prepared through mild hydrothermal me- thod. The initial alkalinity of solutions was thought to play an important role in governing the content of Mn. The effect of substitution Fe^3＋ ions by Mn^3＋ ions on magnetic properties was investigated. The saturation magnetizations of Mn-doped samples are larger than that of corresponding parent compounds due to the moment of Mn^3＋ ion being smaller than that of Fe^3＋. It is clearly shown that incorporation of Mn^3＋ gives rise to significant variations in the Curie temperature. With increasing of Mn content x, Curie temperatures reduced sharply for the garnets, which could be explained by the exchange interaction between a-d Fe^3＋ being reduced in these compounds.

关键词： Hydrothermal synthesis Garnet Substitution ferrimagnetism

A First-Principles Study of Structure-Property Correlation and the Origin of ferrimagnetism in Gallium Ferrite

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Advances in Materials Physics and Chemistry 2012年第4期2卷 1-4页

作者： Amritendu Roy Ashish Garg Rajendra Prasad Sushil Auluck Department of Materials Science and Engineering Department of Physics Indian Institute of Technology Kanpur Kanpur India – 208016 National Physical Laboratory Dr. K. S. Krishnan Marg New Delhi India-110012

A first-principles study of structure property correlation and the origin of ferrimagnetism is presented based on LSDA+U method. In particular, the results for the ground state structure, electronic band structure, density of states, Born effective charges, spontaneous polarization and cationic disorder are discussed. The calculations were done using Vienna ab-initio simulation package (VASP) with projector augmented wave method. We find that the ground state structure is orthorhombic and insulating having A-type antiferromagnetic spin configuration. The cationic disorder is found to play an important role. Although the cationic site disorder is not spontaneous in the ground state, interchange of octahedrally coordinated Ga2 and Fe2 sites is most favored. We find that ferrimagnetism? in gallium ferrite is primarily due to this exchange between Ga-Fe sites? such that Fe spins at Ga1 and Ga2 sites are antiferromagnetically aligned? while maintaining ferromagnetic coupling between Fe spins at Ga1 and Fe1? sites as well as between Fe spins at Ga2 and Fe2 sites. Further, the partial density of states shows noticeable hybridization of Fe 3d, Ga 4s,? Ga 4p and O 2p states indicating some covalent character of Ga/Fe-O bonds.? However, the charge density and electron localization functions show largely the ionic character of these bonds. Our calculation predicts spontaneous polarization of ~59 μC/cm2 along b-axis.

关键词： Gallium Ferrite LSDA+U Spontaneous Polarization ferrimagnetism Cation Site Disorder