Role of interfacial oxidation in the generation of spin-orbit torques
Role of interfacial oxidation in the generation of spin-orbit torques
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DOI：
10.1103/physrevb.102.024405
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发表时间：
2020-04
影响因子：
3.7
通讯作者：
Satoshi Haku;Musha Akira;T. Gao;K. Ando
中科院分区：
文献类型：
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作者：
Satoshi Haku;Musha Akira;T. Gao;K. Ando
我们报道了重金属/铁磁-金属双分子层中电流诱导的自旋轨道转矩（SOTs）被界面附近铁磁层的氧化强烈改变。我们用自旋转矩铁磁共振测量了Pt/Co和$\ mathm {Pt}/{\ mathm {Ni}}_{81}{\ mathm {Fe}}_{19}$ （Pt/Py）薄膜的类阻尼（DL）和类场（FL） SOTs。在Pt/Co薄膜中，我们发现，尽管${\ mathm {CoO}}_{x}$层具有绝缘性质，但靠近界面的Co层的氧化增强了DL和FL SOTs。在$\ mathm {Pt}/{\ mathm {CoO}}_{x}$界面插入薄Ti层后，SOTs的增强消失，表明$\ mathm {Pt}/{\ mathm {CoO}}_{x}/\ mathm {Co}$薄膜中SOTs的主要来源是$\ mathm {Pt}/{\ mathm {CoO}}}_{x}$界面的自旋-轨道耦合。与$\mathrm{Pt}/{\mathrm{CoO}}_{x}/\mathrm{Co}$薄膜不同，$\mathrm{Pt}/{\mathrm{PyO}}_{x}/\mathrm{Py}$薄膜中的SOTs以体自旋-轨道耦合为主。我们的结果表明，Pt/Py薄膜的界面氧化抑制了DL-SOT，并逆转了FL-SOT的符号。SOTs的变化可归因于绝缘层${\ mathm {PyO}}_{x}$的引入引起的自旋混合电导实部和虚部的变化。这些结果表明，界面氧化为控制sot的强度和表征提供了有效的途径。
We report that current-induced spin-orbit torques (SOTs) in heavy-metal/ferromagnetic-metal bilayers are strongly altered by the oxidation of the ferromagnetic layer near the interface. We measured damping-like (DL) and field-like (FL) SOTs for Pt/Co and $\mathrm{Pt}/{\mathrm{Ni}}_{81}{\mathrm{Fe}}_{19}$ (Pt/Py) films using spin-torque ferromagnetic resonance. In the Pt/Co film, we found that the oxidation of the Co layer near the interface enhances both DL and FL SOTs in spite of the insulating nature of the ${\mathrm{CoO}}_{x}$ layer. The enhancement of the SOTs disappears by inserting a thin Ti layer at the $\mathrm{Pt}/{\mathrm{CoO}}_{x}$ interface, indicating that the dominant source of the SOTs in the $\mathrm{Pt}/{\mathrm{CoO}}_{x}/\mathrm{Co}$ film is the spin-orbit coupling at the $\mathrm{Pt}/{\mathrm{CoO}}_{x}$ interface. In contrast to the $\mathrm{Pt}/{\mathrm{CoO}}_{x}/\mathrm{Co}$ film, the SOTs in the $\mathrm{Pt}/{\mathrm{PyO}}_{x}/\mathrm{Py}$ film are dominated by the bulk spin-orbit coupling. Our result shows that the interfacial oxidation of the Pt/Py film suppresses the DL-SOT and reverses the sign of the FL-SOT. The change of the SOTs can be attributed to the change of the real and imaginary parts of the spin mixing conductance induced by the insertion of the insulating ${\mathrm{PyO}}_{x}$ layer. These results show that the interfacial oxidation provides an effective way to manipulate the strength and sign of the SOTs.