Abstract The training effect property of the exchange bias in the reactively sputtered polycrystalline Fe3O4 thin films of varying thicknesses in the range 25–200 nm are studied. Structural studies by X-ray diffraction, X-ray photoelectron spectroscopy and selected area electron diffraction confirm the formation of single phase Fe3O4. The scanning electron spectroscopy images show that the grains are uniformly distributed. All the samples show clear and consistent exchange bias training behaviour due to the dynamics of the spins at the interface of the ferrimagnetic core and the spin glass-like surface of the grains. The analysis of the training effect data of the exchange bias field HE measured at 2 K by using three different models show that the model based on the relaxation of the frozen and rotatable spin components at the interface gives the best description for all the samples. From this model, it is found that the reversible interface spins relax around 7 times faster than the frozen interface spins at 2 K for all the samples and that their relative relaxation rates are independent of the sample thickness. This constancy show that the relative relaxation rates of the interfacial frozen and rotatable spin components is a material dependent property. The frozen component of the interfacial spins of each sample is found to be dominated at the initial stage of the training. A direct equivalence between the HE and remanence asymmetry ME is observed. Above the spin freezing temperature, the training effect measurements at 75 K show that the HE decreases sharply with successive field cycling as compared to the measurements made at 2 K and the HE vanishes after first few cycles.

中文翻译：

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不同厚度溅射沉积Fe 3 O 4 薄膜中交换偏压的训练效果

摘要 研究了反应溅射的多晶 Fe3O4 薄膜在 25-200 nm 范围内不同厚度的交换偏压的训练效应特性。X 射线衍射、X 射线光电子能谱和选区电子衍射的结构研究证实了单相 Fe3O4 的形成。扫描电子能谱图像显示晶粒均匀分布。由于亚铁磁核界面处的自旋动力学和晶粒的自旋玻璃状表面，所有样品都显示出清晰且一致的交换偏置训练行为。使用三种不同模型对 2 K 处测量的交换偏置场 HE 的训练效果数据进行分析表明，基于界面处冻结和可旋转自旋分量的松弛的模型对所有样品给出了最好的描述。从该模型中发现，对于所有样品，可逆界面自旋的弛豫速度比冻结界面在 2 K 时的自旋快 7 倍，并且它们的相对弛豫速率与样品厚度无关。这种恒定性表明界面冻结和可旋转自旋分量的相对弛豫率是一种材料相关特性。发现每个样本的界面自旋的冻结分量在训练的初始阶段占主导地位。观察到 HE 和剩磁不对称 ME 之间的直接等价关系。