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arXiv 2004.12614cond-mat.mtrl-sci
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Mn $_{1+x}$ Fe $_{4-x}$ Si $_{3}$的临界行为和磁热效应

Critical behavior and magnetocaloric effect across the magnetic transition in Mn$_{1+x}$Fe$_{4-x}$Si$_{3}$

Vikram Singh, Pallab Bag, R. Rawat, R. Nath

备注：
18 pages, 13 figures, 1 table
发表信息：
Sci. Rep. 10, 6981 (2020)
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摘要：

详细研究了Mn $_{1+x}$ Fe $_{4-x}$ Si $_{3}$（$ x =$ 0 ~ 1）的磁转变、磁化强度的临界标度和磁热效应的性质。我们的测量结果表明，没有热滞后跨越的磁性转变的母体化合物，这是在与以前的报告，并证实了第二阶性质的过渡。在Fe位Mn的替代可以连续地调谐磁性转变。Mn取代导致晶胞体积线性增加，有效磁矩略有降低。详细的临界分析$x = 0.0$和0.2的磁化数据进行在临界状态下使用修改的Arrott图，Kouvel-Fisher图，通用曲线缩放，和磁热效应的缩放分析。磁化等温线遵循母体化合物（$x=0.0$）的具有临界指数（$β\simeq 0.308$、$γ\simeq 1.448$和$δ\simeq 5.64$）和$x = 0.2$的具有临界指数（$β\simeq 0.304$、$γ\simeq 1.445$和$δ\simeq 5.64$）的改良Arrott图。磁化等温线的Kouvel-Fisher和通用标度图进一步证实了我们的临界分析和指数值的可靠性。这些值的临界指数被发现是相同的母和掺杂的样品不属于任何标准的普适性类。对$x= 0.0$和0.2化合物分别观察到了合理的磁热效应$ΔS_{\rm m}\simeq-6.67$ ~J/Kg-K和-5.84~J/Kg-K，在9 T场变化下观察到了巨大的相对冷却功率（$RCP \sim 700$ ~J/Kg）。磁热效应的普适标度进一步模拟了磁相变的二级特征。由磁热效应临界分析得到的临界指数与由磁等温线分析得到的临界指数一致。

英文摘要：

The nature of the magnetic transition, critical scaling of magnetization, and magnetocaloric effect in Mn$_{1+x}$Fe$_{4-x}$Si$_{3}$ ($ x =$ 0 to 1) are studied in detail. Our measurements show no thermal hysteresis across the magnetic transition for the parent compound which is in contrast with the previous report and corroborate the second order nature of the transition. The magnetic transition could be tuned continuously with Mn substitution at the Fe site. The Mn substitution leads to a linear increase in the unit cell volume and a slight reduction in the effective moment. A detailed critical analysis of the magnetization data for $x = 0.0$ and 0.2 is performed in the critical regime using the modified Arrott plots, Kouvel-Fisher plot, universal curve scaling, and scaling analysis of magnetocaloric effect. The magnetization isotherms follow modified Arrott plots with critical exponent ($β\simeq 0.308$, $γ\simeq 1.448$, and $δ\simeq 5.64$) for the parent compound ($x=0.0$) and ($β\simeq 0.304$, $γ\simeq 1.445$, and $δ\simeq 5.64$) for $x = 0.2$. The Kouvel-Fisher and universal scaling plots of the magnetization isotherms further confirm the reliability of our critical analysis and values of the exponents. These values of the critical exponents are found to be same for both the parent and doped samples which do not fall under any of the standard universality classes. A reasonable magnetocaloric effect $ΔS_{\rm m}\simeq-6.67$~J/Kg-K and -5.84~J/Kg-K for $x= 0.0$ and 0.2 compounds, respectively, with a huge relative cooling power ($RCP \sim 700$~J/Kg) for 9~T field change is observed. The universal scaling of magnetocaloric effect further mimics the second order character of the magnetic transition. The obtained critical exponents from the critical analysis of magnetocaloric effect agree with the values deduced from the magnetic isotherm analysis.

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