Stability of the first-order character of phase transition in HoCo${}_2$

Abstract

HoCo${}_2$ 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 HoCo${}_2$ 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 ($\Delta S_{\mathrm{M}}\propto$ H${}^n$) and the breakdown of universal behavior in the temperature dependence of $\Delta S_{\mathrm{M}}$ 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.

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• Multiple magnetic interactions and large inverse magnetocaloric effect in TbSi and TbSi${}_{0.6}$Ge${}_{0.4}$
• The influence of Ga doping on magnetic properties, magnetocaloric effect, and electronic structure of pseudo-binary GdZn1-xGax (x = 0-0.1)

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