Exchange bias (EB) is normally created by the interfacial exchange coupling at a ferromagnetic/antiferromagnetic (FM/AFM) interface. FM/AFM interfaces have also been proved to perform enhanced spin angular momentum transfer efficiency in spin pumping (SP), compared with typical FM/nonmagnetic interfaces. Here, we report an unexpected EB and enhanced SP between a ferromagnet and semiconductor. Considerable EB has been observed in Co films grown on ZnO single crystal due to the interface antiferromagnetism of the Zn1−xCoxO (x depends on the Co solubility limit in ZnO) layer. Moreover, SP measurements demonstrate a giant spin pumping efficiency at the Co/ZnO interface with a bump (spin mixing conductance Geff↑↓= 28 nm−2) around the blocking temperature TB ∼ 75 K. The enhanced SP is further confirmed by inverse spin Hall effect measurements and the spin Hall angle θISHE of Zn1−xCoxO is estimated to be 0.011. The bound magnetic polarons with s–d exchange interaction between donor electrons and magnetic cation ions in Zn1−xCoxO play a key role in the formation of antiferromagnetism with giant Geff↑↓. Our work provides a new insight into spin physics at FM/semiconducting interfaces.

中文翻译：

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由于 Co/ZnO 界面处的稀释磁性氧化物，非常规的交换偏压和增强的自旋泵效率


交换偏压 （EB） 通常是由铁磁/反铁磁 （FM/AFM） 界面上的界面交换耦合产生的。与典型的 FM/非磁性接口相比，FM/AFM 接口还被证明可以在自旋泵浦 （SP） 中实现增强的自旋角动量传递效率。在这里，我们报告了铁磁体和半导体之间意外的 EB 和增强的 SP。由于 Zn1−xCoxO（x 取决于 ZnO 中的 Co 溶解度极限）层的界面反铁磁性，在 ZnO 单晶上生长的 Co 薄膜中观察到相当大的 EB。此外，SP 测量表明，在 Co/ZnO 界面处具有巨大的自旋泵浦效率，在封闭温度 TB ∼ 75 K 附近有一个凸起（自旋混合电导 Geff↑↓= 28 nm-2）。反自旋霍尔效应测量进一步证实了增强的 SP，Zn1−xCoxO 的自旋霍尔角 θISHE 估计为 0.011。Zn1−xCoxO 中供体电子和磁阳离子之间与 s-d 交换相互作用的束缚磁极化子在巨型 Geff↑↓ 的反铁磁性形成中起关键作用。我们的工作为 FM/半导体界面的自旋物理学提供了新的见解。