Emerging mechanisms of magnetocaloric effect in phase-separated metals

TL;DR

This paper investigates the magnetocaloric effect in phase-separated metallic systems with various magnetic orders, analyzing how phase boundaries and magnetic transitions influence entropy change and the potential for magnetic cooling applications.

Contribution

It introduces a mean-field Hubbard model approach to analyze phase separation effects on magnetocaloric properties in metals with different magnetic orders, revealing new insights into entropy behavior.

Findings

Phase boundaries split the PS region, affecting entropy change.

A kink and linear growth in entropy change occur across phase boundaries.

Second-order magnetic transition impacts entropy despite zero net magnetization.

Abstract

We present a study of the magnetocaloric effect in metallic systems exhibiting first-order magnetic transitions and focus on consequences of magnetic phase separation. We account for ferrimagnetic, ferromagnetic, and Neel antiferromagnetic order. Based on the archetypal Hubbard model being treated within the mean-field approximation, we provide and explore its implications on the field-induced entropy change in metallic system with phase separation. Chosen framework allows us to properly analyze phase volumes' dependence on parameters of phase-separated (PS) system. Moreover, an account for phase separation boundaries as functions of magnetic field provides a natural splitting of the PS region, where each subregion corresponds to a different temperature dependence of entropy change: moving from one subregion to the other produces a kink, followed by a strong linear growth of entropy change. We encounter a second-order magnetic transition from paramagnetic to antiferromagnetic phase in PS region that occurs for particular parameter values. Despite the fact that both phases have zero total magnetization, the transition has a strong impact on entropy change.