Cluster glass transition and relaxation in the random spinel CoGa2O4

arXiv: Strongly Correlated Electrons Pub Date : 2020-10-26 DOI:10.1103/PhysRevB.103.224408

T. Naka, T. Nakane, S. Ishii, M. Nakayama, A. Ohmura, F. Ishikawa, A. de Visser, H. Abe, T. Uchikoshi

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引用次数: 3

Abstract

We report magnetic properties in the random spinel magnet CoGa2O4. Rietveld analysis of the x-ray diffraction profile for CoGa2O4 reveals that the Co and Ga ions are distributed randomly in the tetrahedral A-sites and octahedral B-sites in the cubic spinel structure. CoGa2O4 exhibits a spin-glass transition at TSG = 8.2 K that is confirmed by measurements of the dc- and ac-susceptibilities and thermoremanent magnetization (TRM) that develops below TSG. From the frequency dependence of the freezing temperature Tf for CoGa2O4, it is indicated that the relaxation time follows a Vogel-Fulcher law. Magnetic entropy is considerably reduced, probably because magnetic cluster formation developed even at T > TSG. The relaxation rate of TRM is considerably enhanced at TSG and decays rapidly above and below TSG. The time course of TRM is reproduced by non-exponential relaxation forms, such as a stretched exponential (Kohlrausch) as well as Ogielski and Weron relaxation forms. This behavior is displayed universally in glass systems, and the characteristic parameters associated with these functions were reasonable.

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随机尖晶石CoGa2O4中的团簇玻璃化转变和弛豫

本文报道了随机尖晶石磁体CoGa2O4的磁性能。对CoGa2O4 x射线衍射谱的Rietveld分析表明，Co和Ga离子在立方尖晶石结构中随机分布在四面体a位和八面体b位上。CoGa2O4在TSG = 8.2 K时表现出自旋玻璃化转变，这是通过测量直流和交流磁化率以及在TSG以下产生的热磁化(TRM)来证实的。从CoGa2O4冻结温度Tf的频率依赖性来看，弛豫时间遵循Vogel-Fulcher定律。磁熵显著降低，这可能是因为即使在T > TSG时也形成了磁团簇。TRM弛豫速率在TSG处显著增强，在TSG以上和以下迅速衰减。TRM的时间过程由非指数弛豫形式再现，如拉伸指数弛豫形式(Kohlrausch)以及Ogielski和Weron弛豫形式。这种行为在玻璃系统中普遍存在，与这些功能相关的特征参数是合理的。

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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arXiv: Strongly Correlated Electrons

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