The Correlation between the Covalent Bonds and Magnetocaloric Properties of the Mn2-xFexPyGe1-yMz Compounds

Published

October 7, 2021

Author(s)

Haoran Zhang, Danmin Liu, Zhenlu Zhang, Shaobo Wang, Ming Yue, Qingzhen Huang, Jeffrey Lynn

Abstract

In recent years, MnFePGe magnetocaloric materials have been widely studied as promising candidates for magnetic refrigeration materials. The Curie temperatures of MnFePGe can be adjusted to around room temperature by changing the element ratio or doping with other elements. Due to its first order magnetic and structural transition, it engenders a large entropy change, but unfortunately also can exhibit a large thermal hysteresis during the phase transition which leads to energy loss and lower refrigeration capability. In this paper, we establish a correlation between the in-plane covalent bonding and Curie temperature (T_C), thermal hysteresis (ΔT_hys), two-phase coexistence zone (ΔT_coex), and entropy change (ΔS_DSC) using 54 Mn_2-xFe_xP_yGe_1-yM_z (M is a metallic or nonmetallic doped element) samples with different components. Neutron diffraction and XRD diffraction data and refinements have been employed to allow detailed electron density calculations of 6 typical samples. We find that the length of the in-plane bonding is correlated with T_C and ΔT_hys, while T_C, ΔT_hys, ΔT_coex and ΔS_DSC have no significant correlation with the length of the interlayer covalent bond. Moreover, we find that ΔT_hys correlates most strongly with the change in the bond length when undergoing the paramagnetic to ferromagnetic phase transition, rather than the absolute value of the bond length. These results provide an understanding of what parameters control the properties, enabling an effective way to tune the composition of magnetic refrigeration materials to tailor magnetocaloric properties for optimal performance.

Citation

Journal of Applied Physics

Volume

130

Issue

13

Pub Type

Journals

Keywords

MnFePGe, Magnetocaloric properties, Neutron Diffraction, Covalent bond, Electron density, Curie temperature, Thermal hysteresis

Citation

Zhang, H. , Liu, D. , Zhang, Z. , Wang, S. , Yue, M. , Huang, Q. and Lynn, J. (2021), The Correlation between the Covalent Bonds and Magnetocaloric Properties of the Mn_2-xFe_xP_yGe_1-yM_z Compounds, Journal of Applied Physics (Accessed April 26, 2024)