Magnetocaloric materials undergoing reversible phase transitions are highly desirable for magnetic refrig-eration applications.(Mn,Fe)2(P,Si)alloys exhibit a giant magnetocaloric effect accompanied by a magne-toelastic transition,while the noticeable irreversibility causes drastic degradation of the magnetocaloric properties during consecutive cooling cycles.In the present work,we performed a comprehensive study on the magnetoelastic transition of the(Mn,Fe)2(P,Si)alloys by high-resolution transmission electron mi-croscopy,in situ field-and temperature-dependent neutron powder diffraction as well as density func-tional theory calculations(DFT).We found a generalized relationship between the thermal hysteresis and the transition-induced elastic strain energy for the(Mn,Fe)2(P,Si)family.The thermal hysteresis was greatly reduced from 11 to 1 K by a mere 4 at.％substitution of Fe by Mo in the Mn1.15Fe0.80P0.45Si0.55 alloy.This reduction is found to be due to a strong reduction in the transition-induced elastic strain energy.The significantly enhanced reversibility of the magnetoelastic transition leads to a remarkable improvement of the reversible magnetocaloric properties,compared to the parent alloy.Based on the DFT calculations and the neutron diffraction experiments,we also elucidated the underlying mechanism of the tunable transition temperature for the(Mn,Fe)2(P,Si)family,which can essentially be attributed to the strong competition between the covalent bonding and the ferromagnetic exchange coupling.The present work provides not only a new strategy to improve the reversibility of a first-order magnetic transition but also essential insight into the electron-spin-lattice coupling in giant magnetocaloric materials.

Xuefei Miao;Yong Gong;Fengqi Zhang;Yurong You;Luana Caron;Fengjiao Qian;Wenhui Guo;Yujing Zhang;Yuanyuan Gong;Feng Xu;Niels van Dijk;Ekkes Brück

MIIT Key Laboratory of Advanced Metallic and Intermetallic Materials Technology,School of Materials Science and Engineering,Nanjing University of Science and Technology,Nanjing 210094,China;Fundamental Aspects of Materials and Energy,Department of Radiation Science and Technology,Delft University of Technology,Mekelweg 15,Delft,JB 2629,Netherlands;Department of Physics,Bielefeld University,Bielefeld 33501,Germany;Helmholtz-Zentrum Berlin für Materialien und Energie,Berlin 12489,Germany;College of Physics,Nanjing University of Aeronautics and Astronautics,Nanjing 210016,China

材料科学技术（英文版）

[1]Xuefei Miao;Yong Gong;Fengqi Zhang;Yurong You;Luana Caron;Fengjiao Qian;Wenhui Guo;Yujing Zhang;Yuanyuan Gong;Feng Xu;Niels van Dijk;Ekkes Brück-.Enhanced reversibility of the magnetoelastic transition in(Mn,Fe)2(P,Si)alloys via minimizing the transition-induced elastic strain energy)[J].材料科学技术（英文版）,2022(08):165-176

magnetoelastic,refrig,toelastic,15Fe0,80P0,45Si0

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