HoCo2 exhibits a giant magnetocaloric (MC) effect at its first-order magnetostructural phase transition around 77~K, and understanding the thermodynamic nature of this transition in response to external magnetic fields is crucial for its MC applications. In this study, we present a comprehensive investigation of specific heat and magnetization measurements of HoCo2 under varying magnetic fields. The specific heat measurements qualitatively indicate a transformation from first- to second-order behavior of this phase transition at higher magnetic fields. However, analysis of the power-law dependence of the magnetic entropy change (ΔSM∝ Hn) and the breakdown of universal behavior in the temperature dependence of ΔSM suggest that the first-order nature remains intact, even up to 7 T. This stability of the first-order nature is further manifested through the distinctive non-linear behavior of modified Arrott plots, with a negative slope in the 6--7 T range.
@article{arxiv.2411.05509,
title = {Stability of the first-order character of phase transition in HoCo$_2$},
author = {Ajay Kumar and Anis Biswas and Yaroslav Mudryk},
journal= {arXiv preprint arXiv:2411.05509},
year = {2025}
}