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Structural and magnetic transition in stainless steel Fe-21Cr-6Ni-9Mn up to 250 GPa

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Chinese Physics B 2015年第6期24卷 451-456页

作者：柳雷侯琪玥张毅敬秋民王志刚毕延徐济安李晓东李延春刘景 National Key Laboratory of Shock Wave and Detonation Physics Institute of Fluid PhysicsChina Academy of Engineering Physics Institute of High Energy Physics Chinese Academy of Science

Stainless steel Fe-21Cr-6Ni-9Mn （SS 21-6-9）, with ~21% Cr, ,~6% Ni, and ~ 9% Mn in weight percentage, has wide applications in extensive fields. In the present study, SS 21-6-9 is compressed up to 250 GPa, and its crystal structures and compressive behaviors are investigated simultaneously using the synchrotron angle-dispersive x-ray diffraction technique. The SS 21-6-9 undergoes a structural phase transition from fcc to hcp structure at ~ 12.8 GPa with neglectable volume collapse within the determination error under the quasi-hydrostatic environment. The hcp structure remains stable up to the highest pressure of 250 GPa in the present experiments. The antiferromagnetic-to-nonmagnetic state transition of hcp SS 21-6-9 with the changes of inconspicuous density and structure, is discovered at ~50 GPa, and revealed by the significant change in c/a ratio. The hcp SS-21-6-9 is compressive anisotropic： it is more compressive in the c-axis direction than in the a-axis direction. Both the equations of states （EOSs） of fcc and hcp SS 21-6-9, which are in accordance with those of fcc and hcp pure irons respectively, are also presented. Furthermore, the c/a ratio of hcp SS 21-6-9 at infinite compression, R∞, is consistent with the values of pure iron and Fe-10Ni alloy.

关键词： Fe-21Cr-6Ni-9Mn structure transition magnetic transition x-ray diffraction

Effects of the Mn/Co ratio on the magnetic transition and magnetocaloric properties of Mn_(1+x)Co_(1-x)Ge alloys

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Chinese Physics B 2011年第8期20卷 411-414页

作者：马胜灿王敦辉轩海成沈凌佳曹庆琪都有为 National Laboratory of Solid State Microstructures and Key Laboratory of Nanomaterials for Jiangsu Province Nanjing University

We have investigated the magnetic transition and magnetocaloric effects of Mn1＋xCo1-xGe alloys by tuning the ratio of Mn/Co. With increasing Mn content, a series of first-order magnetostructural transitions from ferromagnetic to paramagnetic states with large changes of magnetization are observed at room temperature. Further increasing the content of Mn （x = 0.11） gives rise to a single second-order magnetic transition. Interestingly, large low-field magnetic entropy changes with almost zero magnetic hysteresis are observed in these alloys. The effects of Mn/Co ratio on magnetic transition and magnetocaloric effects are discussed in this paper.

关键词： Mn/Co ratio magnetic transition magnetocaloric properties magnetic hysteresis losses

Order of magnetic transition and large magnetocaloric effect in Er_3Co

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Chinese Physics B 2010年第4期19卷 427-431页

作者：沈俊赵金良胡凤霞吴剑峰孙继荣沈保根 Technical Institute of Physics and Chemistry Chinese Academy of Sciences State Key Laboratory for Magnetism Institute of PhysicsChinese Academy of Sciences

We have studied the magnetic and magnetocaloric properties of the Er3Co compound, which undergoes ferromagnetic ordering below the Curie temperature Tc = 13 K. It is found by fitting the isothermal magnetization curves that the Landau model is appropriate to describe the Er3Co compound. The giant magnetocaloric effect （MCE） without hysteresis loss around Tc is found to result from the second-order ferromagnetic-to-paramagnetic transition. The max- imal value of magnetic entropy change is 24.5 J/kg.K with a refrigerant capacity （RC） value of 476 J/kg for a field change of 0-5 T. Large reversible MEC and RC indicate the potentiality of Er3Co as a candidate magnetic refrigerant at low temperatures.

关键词： Er3Co compound magnetocaloric effect magnetic transition

Cation ratio and oxygen defects for engineering the magnetic transition of monodisperse nonstoichiometric zinc ferrite nanoparticles

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Science China Materials 2021年第8期64卷 2017-2028页

作者： Yong Sun Xia Deng Yan Zong Xinghua Li Junwei Zhang Juan Feng Xiao Chi Zhenhua Shi Xinliang Zheng Yong Peng School of Physics Northwest UniversityXi’an 710069China State Key Laboratory of Photon Technology in Western China Energy Northwest UniversityXi’an 710069China School of Life Science and Electron Microscopy Center of Lanzhou University Lanzhou UniversityLanzhou 730000China Key Laboratory of Magnetism and magnetic Materials of the Ministry of Education Lanzhou UniversityLanzhou 730000China National University of Singapore Singapore Synchrotron Light Source5 Res LinkSingapore 117603Singapore School of Science Xi’an Technological UniversityXi’an 710021China

Monodisperse nonstoichiometric zinc ferrite nanoparticles with a tunable size of 4.1–32.2 nm are fabricated via thermal decomposition. An extrinsic impurity phase of the ZnO component is present in the zinc ferrite nanoparticles with a size of magnetic transition from superparamagnetism to ferromagnetism. The X-ray magnetic circular dichroism spectra reveal that the spin magnetic moments of Fe^(3+)are reduced, and the orbital magnetic moments are frozen with the increasing atom ratio of Zn/Fe. Therefore,saturation magnetization decreases. The saturation magnetizations of all the zinc ferrite nanoparticles decrease after the air annealing treatment, suggesting that oxygen vacancies considerably influence the magnetic properties. The air annealing treatment can minimize the number of oxygen defects,which trigger some of the Fe^(3+)–OV–Fe^(3+)ferrimagnetic couplings to transfer into the Fe^(3+)–O^(2-)–Fe^(3+)antiferromagnetic couplings. This work provides new insights regarding the magnetic performance of spinel ferrites by tuning the stoichiometric ratio and oxygen defects.

关键词： zinc ferrite nonstoichiometric magnetic transition oxygen defects

Electron Concentration Dependence of Transformation Temperature in Different NiMnGa Alloys with First Order magnetic transition

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Journal of Rare Earths 2005年第4期23卷 I0012-I0012页

作者： Duan Jingfang Zhang Zeyu Wang Dong Long Yi YeRongchang Chang Yongqin School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083China

Composition and electron concentration dependence of transformation temperature in Ni2＋x＋y Mn1-xGa1-y, Ni2＋x Mn1-x Ga alloys with first order magnetic transition were studied. For Ni2 ＋ x ＋ y Mn1- x Ga1-y alloys, martensitic transformation temperature TM increases and Curie temperature Tc decreases with the increase of electron concentration e/a, they intercept at e/a = 7.68. TM and Tc decrease when continue to increase electron concentration. While for Ni2＋x Mn1-xGa alloys, they cross at e/a = 7. 635. Before their crossing, the change tendency with e/a is the same as Ni2＋x＋yMn1-xGa1-y alloys;, after their crossing, both TM and Tc increase slowly. The different relations between TM and Tc and e/a within two NiMnGa alloys show that TM and Tc depend not only on e/a, but also on composition.

关键词： NiMnGa alloys electron concentration (e/a) martensitic transformation magnetic transition rare earths

magnetic transitions in graphene derivatives

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Nano Research 2014年第10期7卷 1507-1518页

作者： Pengzhan Sun Kunlin Wang Jinquan Wei Minlin Zhong Dehai Wu Hongwei Zhu School of Materials Science and Engineering State Key Laboratory of New Ceramics and Fine Processing Key Laboratory of Materials Processing Technology of MOE Tsinghua University Beijing 100084 China Department of Mechanical Engineering Tsinghua University Beijing 100084 China Center for Nano and Micro Mechanics Tsinghua University Beijing 100084 China

The magnetic transitions in graphene oxide （GO） have been investigated experimentally. Micron-sized GO flakes exhibit dominant diamagnetism accompanied by weak ferromagnetism at room temperature. However, when the lateral dimensions of GO flakes are reduced from micron-size to nano-size, a clear transition from dominant diamagnetism to ferromagnetism is observed. After reducing the GO chemically or thermally, the dominant magnetic properties are not altered markedly except for the gradual enhancement of ferromagnetic components. In contrast, at 2 K, significant paramagnetism is present in both the micron-sized and nano-sized GO sheets. The effects of different functional groups on magnetic transitions in graphene derivatives have been further investigated using on hydroxyl-, carboxyl-, amino- and thiol- functionalized graphene. The results reveal that significant diamagnetism with weak ferromagnetism is present at room temperature in all of these functionalized graphene derivatives and the ability of different functional groups to introduce magnetic moments follows the order -SH 〉 --OH 〉 -COOH, -NH2. Notably, at 5 K, diamagnetism, paramagnetism and ferromagnetism coexist in thiol-, hydroxyl- and carboxyl-functionalized graphene, while amino-graphene exhibits dominant paramagnetism, analogous to the low-temperature magnetism in GO. These results indicate that diamagnetism, paramagnetism and ferromagnetism can coexist in graphene derivatives and magnetic transitions among the three states can be achieved which depend on edge states, vacancies, chemical doping and the attached functional groups. The results obtained may help settle the current controversy about the magnetism of graphene-related materials.

关键词： graphene derivatives defects functionalization magnetic transition

Phase transition and magnetocaloric effect of Ni_(55.2)Mn_(18.6)Ga_(26.2-x)Gd_x (x=0,0.05,0.15) alloys

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Journal of Rare Earths 2009年第5期27卷 875-878页

作者：鲍博龙毅段静芳吴光恒叶荣昌万发荣 School of Materials Science and Engineering University of Science and Technology Beijing Institute of Physics Chinese Academy of Sciences

Phase transition process and magnetic entropy change -Delta S of Ni55.2Mn18.6Ga26.2-xGdx(x=0, 0.05, 0.15) alloys were studied. Ni55.2Mn18.6Ga26.2-xGdx(x=0, 0.05, 0.15) alloys still underwent simultaneous structural and magnetic transitions and transform from ferro-magnetic martensitic phase to paramagnetic austenitic phase during heating. Under a field of 2 T, the maximum magnetic entropy change -Delta S-M of Ni55.2Mn18.6Ga26.15Gd0.05 alloy was 7.7 J/kg.K at 317 K during heating and 8.6 J/kg.K at 314 K during cooling while it was 11.8 J/kg.K at 317 K in Ni55.2Mn18.6Ga26.05Gd0.15 alloy during heating.

关键词： NiMnGa magnetocaloric effect (MCE) magnetic transition structural transition magnetic entropy change rare earths

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电场可逆调控二维单层氧化物磁电性能研究

Science Bulletin 2023年第15期68卷 1632-1639,M0004页

作者：王国鹏胡涛熊奕敏刘学沈胜春王建林车梦倩崔璋璋张莹莹杨鲁懿李正操陆亚林田明亮 School of Physics and Optoelectronics Engineering Anhui UniversityHefei 230601China Hefei National Laboratory Hefei 230028China Information Materials and Intelligent Sensing Laboratory of Anhui Province Institutes of Physical Science and Information TechnologyAnhui UniversityHefei 230601China Department of Physics University of Science and Technology of ChinaHefei 230026China Hefei National Research Center for Physical Sciences at the Microscale University of Science and Technology of ChinaHefei 230026China Anhui Laboratory of Advanced Photon Science and Technology University of Science and Technology of ChinaHefei 230026China State Key Laboratory of Low Dimensional Quantum Physics Department of PhysicsTsinghua UniversityBeijing 100084China State Key Laboratory for New Ceramics and Fine Processing Key Laboratory of Advanced Materials of Ministry of EducationSchool of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

具有原子层厚度的氧化物磁性材料拥有将二维磁性应用到下一代自旋电子学新兴领域的巨大潜力,引起了研究者的广泛关注.因此,实现二维单层氧化物磁、电性能的磁场和电场调控,为未来低功耗自旋电子器件提供了广阔应用前景.然而,电场调控二... 详细信息

具有原子层厚度的氧化物磁性材料拥有将二维磁性应用到下一代自旋电子学新兴领域的巨大潜力,引起了研究者的广泛关注.因此,实现二维单层氧化物磁、电性能的磁场和电场调控,为未来低功耗自旋电子器件提供了广阔应用前景.然而,电场调控二维单层氧化物磁性报道很少.本工作利用离子液体门电压进行质子掺杂,实现了对二维单层氧化物(SrRuO_(3))_(1)/(SrTiO_(3))_(N)(N=1,3)磁、电性能的电场可逆调控.随着质子掺杂浓度提高,在(SrRuO_(3))_(1)/(SrTiO_(3))_(1)中观察到了从铁磁金属到反铁磁绝缘态相变,并伴随着磁各向异性的转变.理论分析表明,质子掺杂引起的能带结构改变是结构和磁、电性能相变的主要原因.同时,SrTiO_(3)层起到质子筛作用,在质子的演化过程中扮演重要角色.该研究通过电场调控二维单层氧化物的结构和物性,为实现材料的多功能性提供了重要思路,同时也为实现低功耗功能器件提供了应用潜力.

关键词： Electric-field control 2D oxide monolayer magnets magnetic transition Proton sieve

Reversible magnetism transition at ferroelectric oxide heterointerface

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Science Bulletin 2020年第24期65卷 2094-2099,M0005页

作者： Jialu Chen Zijun Zhang Liang Luo Yunhao Lu Cheng Song Di Cheng Xing Chen Wei Li Zhaohui Ren Jigang Wang He Tian Ze Zhang Gaorong Han State Key Laboratory of Silicon Materials School of Materials Science and EngineeringCyrus Tang Center for Sensor Materials and ApplicationZhejiang UniversityHangzhou 310027China Center of Electron Microscope School of Materials Science and EngineeringZhejiang UniversityHangzhou 310027China Department of Physics and Astronomy Iowa State University and Ames Laboratory-USDOEAmes1A 50011USA Department of Physics Zhejiang UniversityHangzhou 310027China Key Laboratory of Advanced Materials(Ministry of Education) School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

Oxide heterointerface is a platform to create unprecedented two-dimensional electron gas, superconductivity and ferromagnetism, arising from a polar discontinuity at the interface. In particular, the ability to tune these intriguing effects paves a way to elucidate their fundamental physics and to develop novel electronic/magnetic devices. In this work, we report for the first time that a ferroelectric polarization screening at SrTiO_(3)/PbTiO_(3) interface is able to drive an electronic construction of Ti atom, giving rise to room-temperature ferromagnetism. Surprisingly, such ferromagnetism can be switched to antiferromagnetism by applying a magnetic field, which is reversible. A coupling of itinerant electrons with local moments at interfacial Ti3d orbital was proposed to explain the magnetism. The localization of the itinerant electrons under a magnetic field is responsible for the suppression of magnetism. These findings provide new insights into interfacial magnetism and their control by magnetic field relevant interfacial electrons promising for device applications.

关键词： SrTiO3/PbTiO3 Interface Ferroelectric polarization magnetic transition