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Chinese Chemical Letters 2024年第3期35卷 523-527页

作者： Pengfei Tan Chuanhui Zhu Jinjin Yang Shuang Zhao Tao Xia Mei-Huan Zhao Tao Han Zheng Deng Man-Rong Li Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education School of ChemistrySun Yat-sen UniversityGuangzhou 510006China School of Science and Engineering The Chinese University of Hong KongShenzhen 518172China Institute of Physics Chinese Academy of SciencesBeijing 100190China School of Science Hainan UniversityHaikou 570228China

The intricate correlation between multiple degrees of freedom and physical properties is a fascinating area in solid state chemistry and condensed matter physics.Here,we report a quantum-magnetic system BaNi_(2)V_(2)O_(8)(BNVO),in which the spin correlation was modulated by unusual oxidation state,leading to different magnetic behavior.The BNVO was modified with topochemical reduction(TR)to yield TR-BNVO with partially reduced valance state of Ni^(+)in the two-dimensional NiO_(6)-honeycomb lattice.Accordingly,the antiferromagnetic order is suppressed by the introduction of locally interposed Ni^(+)and oxygen vacancies,resulting in a ferromagnetic ground state with the transition temperature up to 710 K.A positive magnetoresistance(7.5%)was observed in the TR-BNVO at 40 K under 7 T.These findings show that topological reduction is a powerful approach to engineer low-dimensional materials and accelerate the discovery of new quantum magnetism.

关键词： Layered honeycomb oxide Topochemical reduction Oxygen vacancies ferromagnetism Magnetoresistance

Recent progress in MnBi2nTe3n+1 intrinsic magnetic topological insulators: crystal growth, magnetism and chemical disorder

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National Science Review 2024年第2期11卷 65-80页

作者： Chaowei Hu Tiema Qian Ni Ni Department of Physics and Astronomy and California Nano Systems Institute University of California-Los Angeles

The search for magnetic topological materials has been at the forefront of condensed matter research for their potential to host exotic states such as axion insulators, magnetic Weyl semimetals, Chern insulators,etc. To date, the MnBi2nTe3n+1family is the only group of materials showcasing van der Waals-layered structures, intrinsic magnetism and non-trivial band topology without trivial bands at the Fermi level. The interplay between magnetism and band topology in this family has led to the proposal of various topological phenomena, including the quantum anomalous Hall effect, quantum spin Hall effect and quantum magnetoelectric effect. Among these, the quantum anomalous Hall effect has been experimentally observed at record-high temperatures, highlighting the unprecedented potential of this family of materials in fundamental science and technological innovation. In this paper, we provide a comprehensive review of the research progress in this intrinsic magnetic topological insulator family, with a focus on single-crystal growth, characterization of chemical disorder, manipulation of magnetism through chemical substitution and external pressure, and important questions that remain to be conclusively answered.

关键词： MnBi2Te4 magnetic topological insulator magnetism tuning antiferromagnetism ferromagnetism pressure chemical doping

Controllable high Curie temperature through 5d transition metal atom doping in CrI_(3)

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Chinese Physics B 2024年第1期33卷 702-707页

作者：彭雪兵司明苏高大强 School of Physical Science and Technology Lanzhou UniversityLanzhou 730000China School of Materials and Energy Lanzhou UniversityLanzhou 730000China

Two-dimensional(2D) CrI_(3) is a ferromagnetic semiconductor with potential for applications in spintronics. However,its low Curie temperature(T_(c)) hinders realistic applications of CrI3. Based on first-principles calculations, 5d transition metal(TM) atom doping of CrI_(3)(TM@CrI_(3)) is a universally effective way to increase T_(c), which stems from the increased magnetic moment induced by doping with TM atoms. T_(c) of W@CrI_(3) reaches 254 K, nearly six times higher than that of the host CrI_(3). When the doping concentration of W atoms is increased to above 5.9%, W@CrI_(3) shows room-temperature ferromagnetism. Intriguingly, the large magnetic anisotropy energy of W@CrI_(3) can stabilize the long-range ferromagnetic order. Moreover, TM@CrI_(3) has a strong ferromagnetic stability. All TM@CrI_(3) change from a semiconductor to a halfmetal, except doping with Au atom. These results provide information relevant to potential applications of CrI_(3) monolayers in spintronics.

关键词： ferromagnetism magnetic anisotropy energy Curie temperature half-metal

ferromagnetism in sp^(2) carbon

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Nano Research 2023年第12期16卷 12883-12900页

作者： Wenxiang Wang Julienne Impundu Jiyou Jin Zhisheng Peng Hui Liu Zheng Wei Yushi Xu Yu Wang Jiawang You Weimin Fan Yong Jun Li Lianfeng Sun CAS Key Laboratory of Nanosystem and Hierarchical Fabrication Nanofabrication laboratoryCAS Center for Excellence in NanoscienceNational Center for Nanoscience and TechnologyBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China The GBA National Institute for Nanotechnology Innovation Guangzhou 510700China

The bulk,pristine sp^(2) carbons,such as graphite,carbon nanotubes,and graphene,are usually assumed to be typical diamagnetic materials.However,over the past two decades,there have been many reports about the ferromagnetism in these sp^(2) carbon materials,which have attracted intense interest for basic research and potential applications.In this review,we focus on the evidence and developments of the emergent ferromagnetism in sp^(2) carbon revealed by nine kinds of experimental methods:magnetic force microscopy(MFM),magnetization measurements with physical property measurement system(PPMS),X-ray magnetic circular dichroism(XMCD),scanning tunneling microscopy(STM),miniaturized magnetic particle inspection(MPI),anomalous Hall effect(AHE),mechanical deflection of carbon nanotube cantilevers,magnetoresistance,and spin-related devices(spin field effect transistor and spin memory).The advantages,conclusions,challenges,and future of these methods are discussed.The ferromagnetism in sp^(2) carbon will open a door to explore exotic physical phenomena and lay the basis for the development of integrated circuit of spintronics,which is fundamentally different from charge-based conventional electronics.

关键词： ferromagnetism sp^(2)carbon anomalous Hall effect spin devices magnetoresistance

ferromagnetism of Ni-Doped ZnO Powders Prepared by Sol-Gel Method above Room Temperature

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Journal of Rare Earths 2006年第Z1期24卷 186-188页

作者： Li Binbin Zhang Rong Xiu Xiangqian Tao Zhikuo Chen Lin Xie Zili Zheng Youdou Yu Huiqiang Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials Department of Physics Nanjing University Nanjing 210093 China Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials Department of Physics Nanjing University Nanjing 210093 China Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials Department of Physics Nanjing University Nanjing 210093 China Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials Department of Physics Nanjing University Nanjing 210093 China Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials Department of Physics Nanjing University Nanjing 210093 China Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials Department of Physics Nanjing University Nanjing 210093 China Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials Department of Physics Nanjing University Nanjing 210093 China Modern Analysis Center Nanjing University Nanjing 210093 China

The magnetic and structural properties of 2% Ni-doped ZnO powers prepared by sol-gel method were studied. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) of the sample do not show existence of any signal of second phase. The X-photoelectron spectroscopy (XPS) of the sample shows the chemical valence of Ni is +2 and the real Ni concentration is 2.19% determined by X-ray fluorescence spectra (XRFS). The magnetic property performed with superconducting quantum interference device (SQUID) shows that the sample exhibits ferromagnetism above room temperature and the Curie temperature (TC) is about 600 K.

关键词： sol-gel Ni-doped ZnO powder ferromagnetism

ferromagnetism and magnetostructural coupling in V-doped MnNiGe alloys

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Chinese Physics B 2018年第10期27卷 565-569页

作者：杨慧刘俊李超王广龙龚元元徐锋 MIIT Key Laboratory of Advanced Metallic and Intermetallic Materials Technology School of Materials Science and EngineeringNanjing University of Science and Technology

The magnetostructural coupling between magnetic and structure transitions plays an important role in the multifunctional applications of magentocaloric materials. In this work, ferromagnetism and magnetostructural transformation are achieved in nonmagnetic V-doped MnNiGe alloys. With simultaneously reducing the transformation temperature and converting antiferromagnetic martensite to ferromagnetic state, the magnetostructural transformation between ferromagnetic orthorhombic phase and paramagnetic hexagonal phase is established in a temperature region as large as 130 K. The magnetic-field-induced magnetostructural transformation is accompanied by considerable magnetocaloric effect.

关键词： magnetostructural transformation ferromagnetism magnetocaloric effect

ferromagnetism in one-dimensional Hubbard model induced by the next-nearest-neighbor hopping at electron density 3/2

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Chinese Physics B 2014年第11期23卷 450-453页

作者：杨媛媛张健潘晖王海龙 State Key Laboratory of Software Development Environment and Department of Physics Beijing University of Aeronautics and Astronautics

ferromagnetism in the one-dimensional Hubbard model with the next-nearest-neighbor hopping is explored by using the exact-diagonalization method in a small cluster and the equation-of-motion method in the thermodynamic limit with electron density n = 3/2. With these two complementary methods, it is found that an intermediate value of the next-nearest- neighbor hopping amplitude tl tends to stabilize the fully polarized ferromagnetic state under the condition that the on-site coulomb interaction U is sufficiently large in our model. The ground-state phase diagram of the model is presented in the tl-U plane.

关键词： ferromagnetism frustration effect random phase approximation

ferromagnetism on a paramagnetic host background in cobalt-doped Bi_2Se_3 topological insulator

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Chinese Physics B 2014年第7期23卷 579-583页

作者：张敏吕莉魏占涛羊新胜赵勇 Key Laboratory of Advanced Technology of Materials of Ministry of Education Superconductor and New Energy R&D CenterSouthwest Jiaotong University Superconductivity Research Group School of Materials and EngineeringUniversity of New South Wale

Cobalt-doped Bi2Se3 topological insulators have been grown though melt-grown reaction. The Bi2Se3 matrix is diamagnetic and doped sample is a superposition of ferromagnetism （FM） and paramagnetism （PM） behavior at low tem- perature. The values of Msmol, Hc, and Mr increase as the Co concentration increases. Two possible explanations have been proposed for the origin of ferromagnetism in Co-doped Bi2Se3. One is the magnetic ordering from nanoclusters of Co-Se compound in the crystals, and the other is Ruderman-Kittel-Kasuya-Yosida （RKKY） interaction between magnetic impurities.

关键词： topological insulator （TI） ferromagnetism Bi2Se3

ferromagnetism in Eu-doped ZnO films deposited by radio-frequency magnetic sputtering

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Chinese Physics B 2010年第9期19卷 580-583页

作者：谭永胜方泽波陈伟何丕模 Department of Physics Zhejiang University Department of Physics Shaoxing University

This paper reports that Eu-doped ZnO films were successfully deposited on silicon （100） by radio-frequency magnetic sputtering. The x-ray diffraction patterns indicate that Eu substitutes for Zn in the lattice. Ferromagnetic loops were obtained by using superconducting quantum interference device at 10 K and room temperature. No discontinuous change was found in both of the zero-field-cooled and field-cooled curves. The observed ferromagnetism in Eu-doped ZnO can be attributed to a single magnetic phase. The saturation magnetisation decreased remarkably for the Eu-doped ZnO prepared by introducing 5% of oxygen in the sputtering gas or by the post annealing in O2, suggesting that the defects play key roles in the development of ferromagnetism in Eu-doped ZnO films.

关键词： Eu-doped ZnO films ferromagnetism radio-frequency magnetic sputtering

ferromagnetism in Fe-doped CuO nanopowder

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Journal of Semiconductors 2012年第1期33卷 29-31页

作者：赵婧夏庆林李晋闽 Semiconductor Lighting Research and Development Center Institute of Semiconductors Chinese Academy of SciencesBeijing 100083China School of Physics and Electronics Central South University Changsha 410083China

The Fe-doped CuO nanopowder was synthesized by following the standard solid-state reaction method. The structure and magnetic properties of the Fe-doped CuO nanopowder were investigated. X-ray diffraction spec- tra confirmed the monoclinic structure of CuO and no secondary phase was detected, indicating that the Fe ions were incorporated into CuO. The ferromagnetism in Fe-doped CuO was studied and is believed to originate from the interaction between Fe ions and Cu ions via a super-exchange interaction or F-center mediated exchange interaction.

关键词： diluted magnetic semiconductors ferromagnetism Fe-doped CuO