J. Mater. Sci. Technol. ›› 2022, Vol. 103: 165-176.DOI: /10.1016/j.jmst.2021.05.087

• Research Article • Previous Articles     Next Articles

Enhanced reversibility of the magnetoelastic transition in (Mn,Fe)2(P,Si) alloys via minimizing the transition-induced elastic strain energy

Xuefei Miaoa,*(), Yong Gonga, Fengqi Zhangb, Yurong Youa, Luana Caronc,d, Fengjiao Qiane, Wenhui Guoa, Yujing Zhanga, Yuanyuan Gonga, Feng Xua,*(), Niels van Dijkb, Ekkes Brückb   

  1. aMIIT Key Laboratory of Advanced Metallic and Intermetallic Materials Technology, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
    bFundamental Aspects of Materials and Energy, Department of Radiation Science and Technology, Delft University of Technology, Mekelweg 15, Delft, JB 2629, Netherlands
    cDepartment of Physics, Bielefeld University, Bielefeld 33501, Germany
    dHelmholtz-Zentrum Berlin für Materialien und Energie, Berlin 12489, Germany
    eCollege of Physics, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
  • Received:2021-04-18 Revised:2021-05-10 Accepted:2021-05-11 Published:2022-03-20 Online:2021-09-15
  • Contact: Xuefei Miao,Feng Xu
  • About author:xufeng@njust.edu.cn (F. Xu).
    * E-mail addresses: xuefeimiao@njust.edu.cn (X. Miao),

Abstract:

Magnetocaloric materials undergoing reversible phase transitions are highly desirable for magnetic refrigeration applications. (Mn,Fe)2(P,Si) alloys exhibit a giant magnetocaloric effect accompanied by a magnetoelastic 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 microscopy, in situ field- and temperature-dependent neutron powder diffraction as well as density functional 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.

Key words: Magnetocaloric effect, (Mn,Fe)2(P,Si), Hysteresis, Neutron diffraction