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magnetostructural transition and Magnetocaloric Effect in Co-and Ga-doped MnNiSi Alloys

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Magnetostructural Transition and Magnetocaloric Effect in Co...

作者： Kasimov Damir 南京理工大学

学位级别：硕士

The MnM'X-based(M' = Ni or Co,X = Ge or Si)intermetallic compounds have received considerable attention in recent years thanks to their tunable magnetostructural transitions and the associated large magnetocaloric *** a member of MnM'X family,stoichiometric MnNiSi alloy has some interesting structural and magnetic properties,which can result in sufficient flexibility for the design of magnetocaloric ***,MnNiSi-based systems cannot achieve stable magnetostructural coupling through the traditional methods,such as single element doping or applying *** the method of isostructural alloying,magnetostructural coupling has been successfully realized in some MnNiSi-based systems by binary element *** now are mainly focused on obtaining a wide temperature interval where magnetostructural coupling can take place and achieving a large associated magnetocaloric effect,which both are desired in practical *** this work,we decided to introduce Co and Ga atoms into MnNiSi matrix and analyze the structural and magnetic properties of several Mn-Co-Ni-Si-Ga polycrystalline alloys through the use of X-ray diffraction,differential scanning calorimetry and vibrating sample *** work includes study of structural properties,structural phase transition temperatures,annealing treatment,magnetic properties and magnetocaloric *** research has shown that the structural transition temperature of Mn1-yCoyNiSi1-xGax(y1 = 0.4,y2 = 0.5),Mno.7Coo.6Nio.7Si1-xGax,Mno.7Coo.7Nio.6Si1-xGax and Mn1-yCo2yNi1-ySi1-xGax(y1 = 0.25,y1 = 0.20,y3 = 0.15)alloys can be efficiently reduced from 1200 K to below room temperature with increasing the Ga content(x).In all studied systems increased substitution level of Co resulted in a stronger stabilization of high-temperature hexagonal *** studying Mn1-yCoyNiSi1-xGax(y1 = 0.4,0.030 ≤x1≤ 0.100;y2 = 0.5,0≤x2≤0.11)alloys,we found that introducing Co only at Mn sites is insufficient t

关键词： MnNiSi-based alloys phase structural transformation magnetostructural transition magnetocaloric effect Curie-temperature window

Large enhancement of magnetocaloric effect induced by dual regulation effects of hydrostatic pressure in Mn_(0.94)Fe_(0.06)NiGe compound

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Journal of Materials Science & Technology 2022年第19期114卷 73-80页

作者： He Zhou Dekun Wang Zhe Li Junzhuang Cong Ziyuan Yu Shuo Zhao Peng Jiang Daoyong Cong Xinqi Zheng Kaiming Qiao Hu Zhang School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China College of Physics and Electronic Engineering Key Laboratory for Advanced Functional and Low Dimensional Materials of Yunnan Higher Education InstituteQujing Normal UniversityQujing 655011China MultiFields Technologies(Beijing)Co.Ltd. Beijing 100190China State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China

MM'X(M,M'=transition metals,X=carbon or boron group elements)compounds could exhibit large magnetocaloric effect due to the magnetostructural transition,and the composition regulation has been widely studied to realize the magnetostructural ***,the magnetostructural transition is also sensitive to the ***,the effect of hydrostatic pressure on magnetostructural transformation and magnetocaloric effect has been investigated in Mn_(0.94)Fe_(0.06)NiGe *** regulation effect of lowering structural transition temperature and strengthening ferromagnetic(FM)state of martensite is realized by applying hydrostatic pressure,which would greatly improve the magnetocaloric effect of Mn_(0.94)Fe_(0.06)NiGe ***,the first-principles calculations have also been performed to discuss the origin of the regulation effect under hydrostatic pressure,and it indicates that the hydrostatic pressure can stabilize the hexagonal structure and decrease the structural transition *** maximum isothermal entropy change increases by 109%from 4.3 J/(kg K)under 0 GPa to 9.0 J/(kg K)under 0.402 GPa for a magnetic field change of 0-3 *** work proves that the hydrostatic pressure is an effective method to regulate the magnetostructural transition and enhance magnetocaloric effect in MM'X compounds.

关键词： Magnetocaloric effect magnetostructural transition Hydrostatic pressure Magnetic properties

Phase transition and mechanical properties of Ni_(30)Cu_(20)Mn_(37+x)Ga_(13-x)(x=0–4.5) alloys

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Rare Metals 2014年第5期33卷 547-551页

作者： Huan-Fang Wang Jing-Min Wang Cheng-Bao Jiang Hui-Bin Xu School of Materials Science and Engineering Beijing University of Aeronautics and Astronautics

Ni30Cu20Mn37＋xGa13-x（x = 0–4.5） alloys were studied with the phase transformation and mechanical properties. With the increase of Mn content, the martensitic transformation temperatures increase and the Curie temperature decreases. Simultaneously, the room temperature microstructure evolves from single phase of austenite to dual phases containing martensite and precipitation. Both the ductility and the strength of the polycrystalline alloys are significantly improved by the precipitation. Coupled magnetostructural transition from weak magnetic martensite to ferromagnetic austenite is obtained in both single-phase and ductile dual-phase alloys.

关键词： Ferromagnetic shape memory alloys(FSMAs) Martensitic transformation magnetostructural transition Mechanical properties

Magnetic phase transitions and magnetocaloric effect in the Fe-doped MnNiGe alloys

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Chinese Physics B 2011年第9期20卷 8-11页

作者：张成亮王敦辉陈健王廷志谢广喜朱纯 School of Science Jiangnan University National Laboratory of Solid State Microstructures and Department of Physics Nanjing University

The magnetic phase transition and magnetocaloric effects in Fe-doped MnNiGe alloys are investigated. The substitution of Fe for Ni decreases the structural transition temperature remarkably, resulting in the magnetostructural transition occurring between antiferromagnetic and ferromagnetic states in MnNil_χFexGe alloy. Owing to the enhanced ferromagnetic coupling induced by the substitution of Fe, metamagnetic behaviour is also observed in TiNiSi-type phase of MnNil-xFezGe alloys at temperature below the structural transition temperature.

关键词： magnetostructural transition metamagnetic magnetocaloric effect

Magnetic phase transition and magnetocaloric effect in Mn_(1-x)Zn_xCoGe alloys

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Chinese Physics B 2014年第9期23卷 428-431页

作者：沈程娟刘强龚元元王敦辉都有为 National Laboratory of Solid State Microstructures and Jiangsu Key Laboratory for Nanotechnology Nanjing University

The magnetic phase transition and magnetocaloric effect are studied in a series of Mn1-xZnxCoGe （x = 0.0l, 0.02, 0.04, and 0.08） alloys. By introducing a small quantity of Zn element, the structural transformation temperature of the MnCoGe alloy is greatly reduced and a first-order magnetostructural transition is observed. Further increasing the Zn concentration results in a second-order ferromagnetic transition. Large room-temperature magnetocaloric effects with small magnetic hysteresis are obtained in alloys with x = 0.01 and 0.02, which suggests their potential application in magnetic refrigeration.

关键词： magnetocaloric effect magnetostructural transition