Systematic ac susceptibility measurements have been performed to study the flux dynamics in a high quality KCa₂Fe₄As₄F₂ single crystal. The irreversible line in the vortex diagram is closed to the Hc2 (T) line suggesting the strong intrinsic pinning in this material. The critical field Hcr = 0.4 T between single vortex pinning state and collective pinning state is obtained according to thermally activated flux creep model. The abnormal behavior in the single vortex pinning region that the activation energy U follows a ∼H−0.53 dependence might arise from the planar defects of submicron scale. The strong field dependences of the activation energy in both regions suggest that artificial pinning centers are needed to enhance the pinning for practical applications. Moreover, the field and current density dependences of the activation energy at relatively high fields are determined as U(J, Hdc ) ∝J−0.26H−1.2 .

中文翻译：

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通过交流磁化率测量研究 KCa2Fe4As4F2 单晶中的通量动力学

已进行系统的交流磁化率测量，以研究高质量 KCa ₂ Fe ₄ As ₄ F ₂单晶中的通量动力学。涡流图中的不可逆线闭合到 HC2个 (吨) 线暗示了这种材料中的强内在钉扎。关键领域 HCr = 0.4 T 在单涡钉扎状态和集体钉扎状态之间是根据热激活通量蠕变模型获得的。单涡钉扎区域的异常行为表明激活能ü跟随一个 ～H−0.53 依赖性可能来自亚微米级的平面缺陷。两个区域中活化能的强场依赖性表明需要人工钉扎中心来增强实际应用中的钉扎。此外，在相对高的场下，活化能的场和电流密度依赖性被确定为ü(杰, HdC ) ∝杰−0.26H−1.2 .