Insight Into the Spin Reorientation Phase Transition in the Magnetocaloric NdNi Compound

Abstract

Exploring and comprehending magnetocaloric materials with spin reorientation (SR) phase transition is of vital importance for practical applications of magnetocaloric effect (MCE). Herein, this study presents a systematic study on the magnetic properties, heat transport properties, magnetic structure, and electronic structure of NdNi compound. NdNi is observed to undergo an SR phase transition and a ferromagnetic (FM) to paramagnetic (PM) phase transition successively with increasing temperature. Neutron powder diffraction (NPD) experiment reveals that the SR phase transition involves the rotation of Nd magnetic moment from a-axis to the direction with a deviation angle θ in ac-plane upon temperature decreasing, whereas Ni does not contribute to the total magnetic moment. These theoretical investigations based on the first-principles calculations and the second-order perturbation theory further confirm that the SR phase transition is closely associated with magnetocrystalline anisotropy energy, which is mainly contributed by Nd atoms. The presence of SR phase transition makes NdNi possess a wide refrigerant temperature span, thus merits it as a magnetic cooling material for applications with various temperature ranges. This work provides profound insights for further exploring and comprehending multiple-phase-transition magnetocaloric materials.