Bose Arnab, Nelson Jocienne N, Zhang Xiyue S, Jadaun Priyamvada, Jain Rakshit, Schlom Darrell G, Ralph Daniel C, Muller David A, Shen Kyle M, Buhrman Robert A
School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, United States.
Department of Physics, Cornell University, Ithaca, New York 14853, United States.
ACS Appl Mater Interfaces. 2020 Dec 9;12(49):55411-55416. doi: 10.1021/acsami.0c16485. Epub 2020 Nov 24.
We report spin-torque ferromagnetic resonance studies of the efficiency of the damping-like (ξ) spin-orbit torque exerted on an adjacent ferromagnet film by current flowing in epitaxial (001) and (110) IrO thin films. IrO possesses Dirac nodal lines (DNLs) in the band structure that are gapped by spin-orbit coupling, which could enable a very high spin Hall conductivity, σ. We find that the (001) films do exhibit exceptionally high ξ ranging from 0.45 at 293 K to 0.65 at 30 K, which sets the lower bounds of σ to be 1.9 × 10 and 3.75 × 10 Ω m, respectively, 10 times higher and of opposite sign than the theoretical prediction. Furthermore, ξ and σ are substantially reduced in anisotropically strained (110) films. We suggest that this high sensitivity to anisotropic strain is because of changes in contributions to σ near the DNLs.
我们报告了自旋扭矩铁磁共振研究结果，该研究针对在外延（001）和（110）氧化铱（IrO）薄膜中流动的电流施加于相邻铁磁体薄膜上的类阻尼（ξ）自旋轨道扭矩效率。氧化铱在能带结构中具有由自旋轨道耦合产生能隙的狄拉克节线（DNLs），这可能导致非常高的自旋霍尔电导率σ。我们发现，（001）薄膜确实表现出异常高的ξ，范围从293 K时的0.45到30 K时的0.65，这分别将σ的下限设定为1.9×10和3.75×10Ω·m，比理论预测值高10倍且符号相反。此外，在各向异性应变的（110）薄膜中，ξ和σ大幅降低。我们认为，这种对各向异性应变的高灵敏度是由于在狄拉克节线附近对σ的贡献发生了变化。
