A Ni80Fe20/alpha-Fe2O3 thin film has been deposited using a dual ion-beam deposition technique where the alpha-Fe2O3 is formed in situ by O-2 bombardment of pure Fe. AC susceptibility results indicate moment fluctuations at temperatures above 150 K. This behavior combined with the thermal fluctuation driven temperature dependence of the negative field coercivity indicates that the alpha-Fe2O3 nanocolumnar crystallite magnetism evolves from static single domain moments to superparamagnetic moments with warming. 25 kOe field cooling establishes exchange bias with an onset temperature of 50 K. The positive (H-c2) and negative (H-c1) field coercivities exhibit very different temperature dependencies, with H-c1(T) well described by a thermally activated coherent domain wall reversal model, while H-c2(T) is essentially constant except for the lowest temperatures. These results point towards different domain reversal mechanisms in positive and negative fields.
展开▼
机译：使用双离子束沉积技术沉积了 Ni80Fe20/α-Fe2O3 薄膜，其中 α-Fe2O3 通过纯 Fe 的 O-2 轰击原位形成。交流磁化率结果表明，在高于 150 K 的温度下会出现力矩波动。这种行为与负场矫顽力的热涨落驱动的温度依赖性相结合，表明α-Fe2O3纳米柱状微晶磁性随着变暖而从静态单畴矩演变为超顺磁矩。25 kOe 场冷却在起始温度为 50 K 时建立交换偏置。正 （H-c2） 和负 （H-c1） 场矫顽力表现出非常不同的温度依赖性，H-c1（T） 由热激活相干畴壁反转模型很好地描述，而 H-c2（T） 除了最低温度外基本上是恒定的。这些结果指出了正场和负场中不同的域反转机制。
展开▼
