We observed an unusual double-shifted hysteresis loop in a perpendicular exchange-coupled Co/IrMn system at room temperature, which leads to an uneven exchange bias field in the positive and the negative field. With the thickness of the antiferromagnetic layer ranging from 4.8 to 10.4 nm, the negative exchange bias field is approximately 100 Oe larger than the positive exchange bias field. This result is related to the density of net spins in the antiferromagnetic layer that have pinned on the ferromagnetic layer. In addition, the exchange bias field of this unusual double-shifted hysteresis loop can be adjusted by the magnetic field annealing temperature.

中文翻译：

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交换偏置垂直 Co/IrMn 系统中不寻常的双移磁化曲线

我们在室温下在垂直交换耦合的 Co/IrMn 系统中观察到不寻常的双移磁滞回线，这导致正负场中的交换偏置场不均匀。反铁磁层的厚度范围为 4.8 至 10.4 nm，负交换偏置场比正交换偏置场大约 100 Oe。该结果与钉扎在铁磁层上的反铁磁层中的净自旋密度有关。此外，这种不寻常的双移磁滞回线的交换偏置场可以通过磁场退火温度进行调整。