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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 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： Hui Yang Jun Liu Chao Li Guang-Long Wang Yuan-Yuan Gong Feng Xu MIIT Key Laboratory of Advanced Metallic and Intermetallic Materials Technology School of Materials Science and EngineeringNanjing University of Science and TechnologyNanjing 210094China

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 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 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 in ZnO with(Mn,Li) codoping

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Chinese Physics B 2013年第3期22卷 421-425页

作者：马世甲芦鹏飞俞重远赵龙李琼瑶武成洁丁路 State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications

First-principles calculations were performed to investigate the magnetic properties of Zn（Mn,Li）O based on the Perdew-Burke-Ernzerhof form of the generalized gradient ***（AFM） ordering is the ground state in Mn-doped ZnO system without the codopant of Li,while seven different geometrical configurations of Zn（Mn,Li）O prefer stable ferromagnetic（FM） *** found that dopant Li can effectively change the magnetic coupling in the ZnMnO *** Curie temperature（TC） of FM ordering depends on the geometric configuration,and the highest T C is about 1388 *** FM stabilization is greatly affected by Mn-Mn distance rather than by the position of dopant *** propose that dopant Li mediates FM coupling through a double exchange interaction or an RKKY interaction when Li is located,respectively,near or far from Mn ions.

关键词： density functional theory ferromagnetism Curie temperature

ferromagnetism in an Itinerant Electron System

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Communications in Nonlinear Science and Numerical Simulation 1996年第3期1卷 12-16页

作者： D. F. WAANG(Institut de Physique Theorique Ecole Polytechnique Federale de Lausanne,PHB-Ecublens, CH-1015 Lausanne, Switzerland)E-mail: wang@sidpsg. epfl.ch Institut de Physique Théorique Ecole Polytechnique Fédérale de Lausanne PHB-Ecublens CH-1015 Lausanne Switzerland

In this work, the ground states of the Hubbard model on complete graph arestudied, for a finite lattice sise L and arbitrary on-site energy U. We construct explicitlythe ground states of the system when the number of the electrons Ne ≥ L + 1. In particular,for Ne = L + 1, the ground state is ferromagntic with total spin sg = (Ne - 2)/2.

关键词： ferromagnetism Hubbard model Kondo-lattice model

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： Zhao Jing Xia Qinglin Li Jinmin 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

Defect induced room-temperature ferromagnetism and enhanced photocatalytic activity in Ni-doped ZnO synthesized by electrodeposition

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Chinese Physics B 2020年第10期29卷 566-572页

作者： Deepika Raju Kumar Ritesh Kumar Kamdeo Prasad Yadav Pratyush Vaibhav Seema Sharma Rakesh Kumar Singh Santosh Kumar College o f Commerce Arts and SciencePatna.BiharIndia Jaypee University o f Engineering and Technology GunaMadhya PradeshIndia Anugrah Narayan College PatnaBiharIndia Aryabhatta Knowledge University PatnaBiharIndia

Zn0.90Ni0.10O nanoparticles have been synthesized by single-bath two-electrode electrodeposition at constant voltage. X-ray diffraction, UV vis and photoluminescence studies reveal that a single-phase polycrystalline hcp wurtzite crystal structure of ZnO is evolved. The material consists of a large number of defects such as oxygen vacancy (Ov) and zinc interstitial (Zi). The magnetization study reveals that the sample exhibits room-temperature global ferromagnetism and the ferromagnetic ordering seems to be defect induced via bound magnetic polaron mechanism, and double exchange is also expected to have played role. Interesting optoelectronic properties have been found in the synthesized sample and the material seems to be a potential candidate to be used as a UV sensor. Such a transition metal doped ZnO based dilute magnetic semiconducting system exhibiting room-temperature ferromagnetism is likely to be first of its kind in the sense that such materials have not yet been reported to be synthesized by the simple method of electrodeposition to the best of our knowledge on the basis of ample literature review.

关键词： dilute magnetic semiconductors(DMS) bound magnetic polaron photoluminescence ferromagnetism