A low-temperature feature is detected in nanogranular magnetic films with perpendicular anisotropy that have a low-field positive magnetoresistance: positive magnetoresistance is observed during the initial magnetization of the demagnetized sample, but is absent when the magnetic field is removed and/or during subsequent magnetizations. This effect is studied using a Cox(Al2On)1−x film with x = 0.60, consisting of Co metal nanogranules in an Al2On insulating matrix with n close to 3. It is found that together with perpendicular anisotropy, the film has local in-plane anisotropy with randomly oriented easy axes, which prevents the reorientation of the granules’ magnetic moment projections in the film plane below a certain blocking temperature. The restoration of the local short-range order in the orientation of the magnetic moments of the demagnetized film’s neighboring granules, which is optimal for conductivity and is destroyed by the introduction of a magnetic field, is prevented at temperatures below the blocking temperature and is not restored during subsequent cycles of introducing/removing the magnetic field without heating to temperatures above the blocking temperature.

中文翻译：

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具有低场正磁阻的纳米颗粒复合材料的磁输运特性

在具有低场正磁阻的具有垂直各向异性的纳米颗粒磁膜中检测到低温特征：在退磁样品的初始磁化过程中观察到正磁阻，但在去除磁场和/或随后的过程中不存在磁化。使用 x = 0.60 的 Cox(Al2On)1-x 膜研究这种效应，该膜由 Al2On 绝缘基质中的 Co 金属纳米颗粒组成，n 接近 3。发现与垂直各向异性一起，该膜具有局部内向性具有随机取向的易轴的平面各向异性，可防止颗粒的磁矩投影在低于特定阻塞温度的薄膜平面中重新定向。