Al₂MnFe Heusler合金的磁临界现象与低温重入自旋玻璃特征
Magnetic critical phenomena and low temperature re-entrant spin-glass features of Al$_2$MnFe Heusler alloy
AI总结：
本文研究了多晶Al₂MnFe Heusler合金的结构和磁性能，发现其具CsCl型结构、122.9 K二阶铁磁相变、3D-Heisenberg型临界行为、重入自旋玻璃特征及与同类体系相当的磁热效应。
摘要：
本文报道了多晶Al₂MnFe Heusler合金的结构和磁性能的详细研究，包括磁热效应、低温重入自旋玻璃行为及临界行为。制备的合金结晶为立方CsCl型晶体结构，空间群为Pm-3m。温度依赖磁化数据显示约122.9 K时发生二阶顺磁到铁磁相变，磁热效应分析进一步证实了这一点。等温磁化曲线表明该合金具有软铁磁行为，且揭示了潜在交换相互作用的 itinerant 特征。为理解磁相互作用本质，利用修正Arrott图、Kouvel-Fisher图和临界等温线分析确定了自发磁化、初始磁化率和临界MH等温线的临界指数。推导的临界指数β=0.363(2)、γ=1.384(3)和δ=4.81(3)证实其临界行为与短程交换相互作用的3D-Heisenberg型铁磁体相似，交换相互作用随距离衰减为J(r)≈r⁻⁴.⁹³⁶。此外，交流磁化率数据的详细分析表明，峰值温度的频率依赖性偏移可用临界慢化模型和Vogel-Fulcher定律很好地解释，证实了Al₂MnFe Heusler合金中存在重入自旋玻璃特征。磁热研究确定，在50 kOe外磁场下，最大磁熵变约为1.92 J/kg-K，相对制冷功率约为496 J/kg，与其他Mn-Fe-Al体系相当。
英文摘要：
A detailed investigation of the structural and magnetic properties, including magnetocaloric effect, re-entrant spin-glass behavior at low temperature, and critical behavior in polycrystalline Al$_2$MnFe Heusler alloy is reported. The prepared alloy crystallizes in a cubic CsCl-type crystal structure with Pm-3m space group. The temperature-dependent magnetization data reveals a second-order paramagnetic to ferromagnetic phase transition ($\sim$ 122.9 K), which is further supported by the analysis of the magnetocaloric effect. The isothermal magnetization loops show a soft ferromagnetic behavior of the studied alloy and also reveal an itinerant character of the underlying exchange interactions. In order to understand the nature of magnetic interactions, the critical exponents for spontaneous magnetization, initial magnetic susceptibility, and critical MH isotherm are determined using Modified Arrott plots, Kouvel-Fisher plots, and critical isotherm analysis. The derived critical exponents $β$ = 0.363(2), $γ$ = 1.384(3), and $δ$ = 4.81(3) confirm the critical behavior similar to that of a 3D-Heisenberg-type ferromagnet with short-range exchange interactions that are found to decay with distance as J(r) $\approx$ r$^{-4.936}$. Moreover, the detailed analysis of the AC susceptibility data suggests that the frequency-dependent shifting of the peak temperatures is well explained using standard dynamic scaling laws such as the critical slowing down model and Vogel-Fulcher law, and confirms the signature of re-entrant spin-glass features in Al$_2$MnFe Heusler alloy. Furthermore, maximum magnetic entropy change of $\sim$ 1.92 J/kg-K and relative cooling power of $\sim$ 496 J/kg at 50 kOe applied magnetic field are determined from magnetocaloric studies that are comparable to those of other Mn-Fe-Al systems.
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