一阶变磁MnCo1-xFexSi熵变的宽温度范围
Wide temperature span of entropy change in first-order metamagnetic MnCo1-xFexSi
摘要：
研究了MnCoxFe_（1-x）Si（x=0-0.5）化合物的晶体结构和磁性。随着Fe含量的增加，晶胞各向异性发生变化，磁性逐渐演化：居里温度不断降低，从低温螺旋反铁磁态到高温铁磁态的一级变磁转变逐渐消失，然后在低温区出现类自旋玻璃态和另一种反铁磁态.居里转变导致适度的常规熵变。变磁转变不仅在较低的外加磁场下产生比MnCoSi更大的负磁热效应，而且还产生非常大的Δ S（T）的温度跨度（对于H=5 T为103 K），这导致大的制冷剂容量。从晶体结构变化和磁弹耦合机制两个方面对这些现象进行了解释。低成本的MnCo 1-xFexSi化合物由于具有大的等温熵变和宽的工作温度范围而成为近室温磁制冷应用的有希望的候选者。
英文摘要：
The crystal structure and magnetic properties of MnCoxFe1-xSi (x=0-0.5) compounds were investigated. With increasing Fe content, the unit cell changes anisotropically and the magnetic property evolves gradually: Curie temperature decreases continuously, the first-order metamagnetic transition from a low-temperature helical antiferromagnetic state to a high-temperature ferromagnetic state disappears gradually and then a spin-glass-like state and another antiferromagnetic state emerge in the low temperature region. The Curie transition leads to a moderate conventional entropy change. The metamagnetic transition not only yields a larger negative magnetocaloric effect at lower applied fields than in MnCoSi but also produces a very large temperature span (103 K for H=5 T) of delta S(T), which results in a large refrigerant capacity. These phenomena were explained in terms of crystal structure change and magnetoelastic coupling mechanism. The low-cost MnCo1-xFexSi compounds are promising candidates for near room temperature magnetic refrigeration applications because of the large isothermal entropy change and the wide working temperature span.
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