Enhanced reversibility of the magnetoelastic transition in (Mn,Fe)2(P,Si) alloys via minimizing the transition-induced elastic strain energy
Xuefei Miao (Nanjing University of Science and Technology)
Yong Gong (Nanjing University of Science and Technology)
Fengqi Zhang (TU Delft - RST/Fundamental Aspects of Materials and Energy)
Yurong You (Nanjing University of Science and Technology)
Luana Caron (Bielefeld University, Helmholtz-Zentrum Berlin)
Fengjiao Qian (Nanjing University of Aeronautics and Astronautics)
Feng Xu (Nanjing University of Science and Technology)
Niels van Dijk (TU Delft - RST/Fundamental Aspects of Materials and Energy)
Ekkes Brück (TU Delft - RST/Fundamental Aspects of Materials and Energy)
undefined More Authors (External organisation)
More Info
expand_more
Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
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.