Hard Ferromagnets as a New Perspective on Materials for Thermomagnetic Power Generation Cycles

TL;DR

This paper explores the potential of hard ferromagnets and artificial spin reorientation materials to enhance thermomagnetic power generation, highlighting experimental and computational insights into their performance and advantages.

Contribution

It introduces the idea of using hard ferromagnets as TMG materials, supported by experiments and simulations, and discusses new material classes like artificial spin reorientation materials.

Findings

Hard ferrites are not yet ideal TMG candidates but could improve with higher thermal conductivity and magnetization change.

Biasing soft magnets with hard ferromagnets shifts the M-H loop, increasing work output.

Artificial spin reorientation materials are proposed as promising new TMG working materials.

Abstract

We consider the ways in which magnetically hard materials can be used as the working materials in thermomagnetic power generation (TMG) cycles in order to expand the area in the magnetisation vs. applied field ($M-H$) plane available for energy conversion. There are 3 parts to this Perspective. First, experiments on commercially available hard ferrites reveal that, while these materials are not yet good TMG candidates, hard ferromagnets with higher thermal conductivity and a greater change of magnetization with temperature could outperform existing TMG materials. Second, computational results indicate that biasing a soft magnet with a hard ferromagnet is essentially equivalent to shifting the $M-H$ loop by an amount proportional to the field of the biasing magnet. Work outputs under biased conditions show a substantial improvement over unbiased cycles, but experimental verification is needed. Third, we discuss the rationale for exploring artificial spin reorientation materials as novel TMG working materials.