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标题：Unusual ferromagnetic critical behavior owing to short-range antiferromagnetic correlations in antiperovskite Cu_1-xNMn_3+x (0.1 ≤ x ≤ 0.4)
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作者：Jianchao Lin ; Peng Tong ; Dapeng Cui 等
期刊名称：Scientific Reports
电子版ISSN：2045-2322
出版年度：2015
卷号：5
DOI：10.1038/srep07933
出版社：Springer Nature
摘要：For ferromagnets, varying from simple metals to strongly correlated oxides,the critical behaviors near the Curie temperature ( T _C) can be grouped into several universal classes. In this paper, we report an unusual critical behavior in manganese nitrides Cu_{1- x}NMn_{3+ x} (0.1 ≤ x ≤ 0.4). Although the critical behavior below T _C can be well described by mean field (MF) theory, robust critical fluctuations beyond the expectations of any universal classes are observed above T _C in x = 0.1. The critical fluctuations become weaker when x increases, and the MF-like critical behavior is finally restored at x = 0.4. In addition, the paramagnetic susceptibility of all the samples deviates from the Curie-Weiss (CW) law just above T _C. This deviation is gradually smeared as x increases. The short-range antiferromagnetic ordering above T _C revealed by our electron spin resonance measurement explains both the unusual critical behavior and the breakdown of the CW law.