We present high frequency measurements of the vortex dynamics of a FeSe$_x$Te$_{1-x}$ ($x=0.5$) thin film grown on a CaF$_2$ substrate and with a critical temperature $T_c\simeq18\;$K, performed by means of a dual frequency dielectric resonator at 16.4 GHz and 26.6 GHz. We extract and discuss various important vortex parameters related to the pinning properties of the sample, such as the characteristic frequency $\nu_c$, the pinning constant $k_p$ and the pinning barrier height $U$ relevant for creep phenomena. We find that the vortex system is in the single-vortex regime, and that pinning attains relatively high values in terms of $k_p$, indicating significant pinning at the high frequencies here studied. The pinning barrier energy $U$ is quite small and exhibits a non-monotonous temperature dependence with a maximum near 12 K. This result is discussed in terms of core pinning of small portion of vortices of size $\propto\xi^3$ jumping out of the pinning wells over very small distances, a process which is favoured in the high frequency, short ranged vortex oscillations here explored.

中文翻译：

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通过表面阻抗的多频测量，FeSeTe 薄膜的钉扎特性

我们展示了在 CaF$_2$ 衬底上生长的 FeSe$_x$Te$_{1-x}$ ($x=0.5$) 薄膜的涡流动力学的高频测量值，并具有临界温度 $T_c\simeq18 \;$K，通过 16.4 GHz 和 26.6 GHz 的双频介电谐振器执行。我们提取并讨论了与样品钉扎特性相关的各种重要涡旋参数，例如特征频率 $\nu_c$、钉扎常数 $k_p$ 和与蠕变现象相关的钉扎势垒高度 $U$。我们发现涡流系统处于单涡流状态，并且钉扎在 $k_p$ 方面达到相对较高的值，表明此处研究的高频处有显着的钉扎。钉扎势垒能量 $U$ 非常小并且表现出非单调的温度依赖性，最大值接近 12 K。