Thermodynamics and entropic inference of nanoscale magnetic structures in Gd.

IF 2.3 4区 物理与天体物理 Q3 PHYSICS, CONDENSED MATTER
Christian Binek, Syed Qamar Abbas Shah, Balamurugan Balasubramanian
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引用次数: 0

Abstract

A bulk gadolinium (Gd) single crystal exhibits virtually zero remnant magnetization, a common trait among soft uniaxial ferromagnets. This characteristic is reflected in our magnetometry data showing virtually hysteresis free isothermal magnetization loops with large saturation magnetization. The absence of hysteresis allows to model the measured easy axis magnetization as a function of temperature and applied magnetic field, rather than a relation, which permits the application of Maxwell relations from equilibrium thermodynamics. Demagnetization effects broaden the isothermal first-order transition from negative to positive magnetization. By analyzing magnetization data within the coexistence regime, we deduce the isothermal entropy change and the field-induced heat capacity change. Comparing the numerically inferred heat capacity with relaxation calorimetric data confirms the applicability of the Maxwell relation. Analysis of the entropy in the mixed phase region suggests the presence of hitherto unresolved nanoscale magnetic structures in the demagnetized state of Gd. To support this prediction, Monte Carlo simulations of a 3D Ising model with dipolar interactions are performed. Analyzing the cluster size statistics and magnetization from the model provides strong qualitative support of our analytic approach.

钆中纳米级磁结构的热力学和熵推断。
块状钆(Gd)单晶体的残余磁化几乎为零,这是软单轴铁磁体的共同特征。这一特性反映在我们的磁力测量数据中,这些数据显示了几乎无磁滞的等温磁化环和较大的饱和磁化。由于不存在磁滞现象,因此可以将测量到的易轴磁化建模为温度和外加磁场的函数,而不是一种关系,这样就可以应用平衡热力学中的麦克斯韦关系。退磁效应拓宽了从负磁化到正磁化的等温一阶转变。通过分析共存体系中的磁化数据,我们推导出了等温熵变和场致热容量变化。将数值推断的热容量与松弛量热数据进行比较,证实了麦克斯韦关系的适用性。对混合相区熵的分析表明,在钆的退磁状态下存在迄今尚未解决的纳米级磁结构。为了支持这一预测,我们对具有双极相互作用的三维伊辛模型进行了蒙特卡罗模拟。从模型中分析簇尺寸统计和磁化为我们的分析方法提供了强有力的定性支持。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Journal of Physics: Condensed Matter
Journal of Physics: Condensed Matter 物理-物理:凝聚态物理
CiteScore
5.30
自引率
7.40%
发文量
1288
审稿时长
2.1 months
期刊介绍: Journal of Physics: Condensed Matter covers the whole of condensed matter physics including soft condensed matter and nanostructures. Papers may report experimental, theoretical and simulation studies. Note that papers must contain fundamental condensed matter science: papers reporting methods of materials preparation or properties of materials without novel condensed matter content will not be accepted.
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