Possibility of vortex lattice structural phase transition in the superconducting pnictide Ba(Fe0.925Co0.075)2As2
Possibility of vortex lattice structural phase transition in the superconducting pnictide Ba(Fe0.925Co0.075)2As2
复制标题
DOI：
10.1103/physrevb.81.092504
复制
发表时间：
2010-03-01
影响因子：
3.7
通讯作者：
Xu, Z. A.
中科院分区：
文献类型：
--
作者：
Kopeliansky, R.;Shaulov, A.;Xu, Z. A.
我们对新发现的超导铁磷化物 Ba(Fe0.925Co0.075)(2)As-2 的单晶进行了磁测量。磁化环表现出第二个磁化峰（SMP），与大多数高温超导体（HTS）中观察到的类似。磁弛豫测量揭示了归一化弛豫率的最小值 S = d ln M/d ln t，位于 SMP 起始点和峰值场之间。 HTS 中的 SMP 通常与涡序-无序相变相关。然而，在 Ba(Fe0.925Co0.075)(2)As-2 中，起始场和峰值场以及 S 中的最低点在低温下表现出强烈的温度依赖性，排除了这种转变的可能性。我们认为，Ba(Fe0.925Co0.075)(2)As-2 中的 SMP 与在对应于 S 最小点的场和温度下发生的从菱形晶格到方晶格的涡旋结构相变有关。基于最近的涡旋结构相变理论模型，对过渡线的理论拟合显示出与实验结果良好的一致性。
We present magnetic measurements in a single crystal of the newly discovered superconducting ironpnictide Ba(Fe0.925Co0.075)(2)As-2. The magnetization loops exhibit a second magnetization peak (SMP) similar to that observed in most high-temperature superconductors (HTSs). Magnetic relaxation measurements reveal a minimum in the normalized relaxation rate, S = d ln M/d ln t, located in between the SMP onset and the peak fields. The SMP in HTSs is commonly associated with the vortex order-disorder phase transition. However, in Ba(Fe0.925Co0.075)(2)As-2 the onset and peak fields, as well as the minimum point in S, exhibit strong temperature dependence down to low temperatures, excluding the possibility for such a transition. We suggest that the SMP in Ba(Fe0.925Co0.075)(2)As-2 is associated with a vortex structural phase transition from rhombic to square lattice taking place at field and temperatures corresponding to the minimum point of S. A theoretical fit to the transition line, based on a recent theoretical model for vortex structural phase transition, shows good agreement with the experimental results.