Analysis of Barkhausen avalanches in thin films of magnetic material has been an active area of research due to the proximity of the dimensionality crossover. However, the measurement of avalanches in ultrathin films (thickness <~ 20 nm) by conventional inductive pick-up methods is challenging due to the small mass of the material involved. Here, we describe an optical method to analyze Barkhausen avalanches in ultrathin magnetic films with a temporal resolution of ~ 10 μs. We measure the avalanche statistics of 15-nm thick film of NiFe grown by pulsed laser ablation, where we observe a breakdown of the power-law probability distributions of s and T as well as a breakdown of the power-law relation between <s(T)> and <T>. The observations could not be explained within the framework of the established front propagation or nucleation models under adiabatic evolution. We attempt to explain our findings by performing simulations of the 2D random field Ising model under non-adiabatic evolution with a constant field step, and obtain good qualitative agreement between experimental and simulated probability distributions for high disorder levels. We conclude that the observed peculiarities are a consequence of strong pinning and the departure from the adiabatic condition during magnetic field sweep.

中文翻译：

---

超薄铁磁膜中巴克豪森临界的破坏

磁性材料薄膜中的巴克豪森雪崩的分析已成为研究的一个活跃领域，这是由于维数交叉的原因。然而，由于涉及的材料的质量小，因此通过常规的感应拾取方法来测量超薄膜（厚度<〜20 nm）中的雪崩是具有挑战性的。在这里，我们描述了一种光学方法，用于分析时间分辨率为〜10 s的超薄磁性膜中的巴克豪森雪崩。我们测量了通过脉冲激光烧蚀生长的15 nm厚NiFe薄膜的雪崩统计数据，其中我们观察到s和T的幂律概率分布的分解以及< s之间的幂律关系的分解（Ť）>和<T>。在绝热演化下建立的正面传播或成核模型的框架内无法解释这些观察结果。我们试图通过对非绝热演化过程中具有恒定场阶的2D随机场Ising模型进行仿真来解释我们的发现，并在高无序水平的实验和模拟概率分布之间获得良好的定性一致性。我们得出的结论是，观察到的特性是强钉扎和磁场扫描期间脱离绝热条件的结果。