标题： HoCo$_2$相变的一阶特性稳定性 显示英文标题

标题： Stability of the first-order character of phase transition in HoCo$_2$

摘要： HoCo$_2$在其一级磁结构相变约77 K时表现出巨大的磁热效应（MC），理解该相变在外部磁场响应下的热力学性质对于其MC应用至关重要。 在本研究中，我们对HoCo$_2$在不同磁场下的比热和磁化测量进行了全面研究。 比热测量定性地表明，在较高磁场下，该相变的行为从一级转变为二级。 然而，磁熵变（$\Delta S_{\rm M} \propto$ H$^n$）的幂律依赖性的分析以及$\Delta S_{\rm M}$温度依赖性的普遍行为的破坏表明，即使在7 T的情况下，一级性质仍然保持不变。这种一级性质的稳定性进一步通过修改后的Arrott图的显著非线性行为表现出来，在6-7 T范围内具有负斜率。 显示英文摘要

摘要： 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 ($\Delta S_{\rm M} \propto$ H$^n$) and the breakdown of universal behavior in the temperature dependence of $\Delta S_{\rm M}$ 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.