Lin Jianchao, Tong Peng, Cui Dapeng, Yang Cheng, Yang Jie, Lin Shuai, Wang Bosen, Tong Wei, Zhang Lei, Zou Youming, Sun Yuping
Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China.
High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, China.
Sci Rep. 2015 Jan 21;5:7933. doi: 10.1038/srep07933.
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.
对于从简单金属到强关联氧化物的铁磁体，居里温度（T(C)）附近的临界行为可分为几个通用类别。在本文中，我们报道了氮化锰Cu(1 - x)NMn(3 + x)（0.1 ≤ x ≤ 0.4）中一种不寻常的临界行为。尽管低于T(C)的临界行为可以用平均场（MF）理论很好地描述，但在x = 0.1时，高于T(C)观察到了超出任何通用类别预期的强烈临界涨落。当x增加时，临界涨落变弱，并且在x = 0.4时最终恢复类似MF的临界行为。此外，所有样品的顺磁磁化率恰好在T(C)之上偏离居里 - 外斯（CW）定律。随着x增加，这种偏差逐渐消失。我们的电子自旋共振测量揭示的高于T(C)的短程反铁磁有序解释了这种不寻常的临界行为和CW定律的失效。
