講演情報
[17p-K102-6]Thickness-dependent magnetization switching induced by spin-orbit torque in Weyl ferromagnet SrRuO3 single-layer films
〇(D)Hiroto Horiuchi1, Wakabayashi Yuki K.2, Araki Yasufumi3, Ieda Jun'ichi3, Yamanouchi Michihiko4, Kaneta-Takada Shingo1, Taniyasu Yoshitaka2, Yamamono Hideki2, Krockenberger Yoshiharu2, Tanaka Masaaki1,5, Ohya Shinobu1,5 (1.The Univ. of Tokyo, 2.NTT BRL, 3.JAEA, 4.Hokkaido Univ., 5.CSRN)
キーワード：
Spin-orbit torque、Weyl ferromagnet、Magnetic memory
The Weyl ferromagnet SrRuO3 (SRO) holds significant potential for developing energy-efficient spin-orbitronics devices. Recently, we have successfully demonstrated spin-orbit torque (SOT)-induced partial magnetization switching in a full-epitaxial high-quality SRO single layer. Although the film appears to be seemingly uniform, our detailed analyses revealed the presence of an inhomogeneous distribution of oxygen octahedral rotation (OOR), with particularly pronounced rotation near the SRO/SrTiO3 (STO) interface. The strong spin Berry curvature induced by the OOR generates a significant intrinsic spin Hall effect (SHE), leading to the magnetization reversal in the SRO layer near the SRO/STO interface. This experiment implies that the switching behavior may vary depending on the film thickness; however, there is no systematic thickness-dependent study of the SOT magnetization switching in SRO.
In this study, we grew SRO films with various thicknesses d of 5, 15, and 26 nm on STO (001) substrates using a machine-learning-assisted molecular beam epitaxy system. Partial SOT magnetization switching was observed in all films. The chirality of the switching hysteresis loops changes by reversing the sign of the in-plane supporting field applied along the current direction, confirming that SOT drives the observed magnetization switching. The switching current density was in the order of MA cm–2, one order of magnitude smaller than conventional ferromagnet/heavy metal bilayer systems, which highlights the potential of SRO for highly efficient switching. The switching ratio was found to increase in SRO films with larger d. For example, when d = 15 nm, the switching ratio is approximately 3.5 (=11%/3.1%) times larger than when d = 5 nm.
In this study, we grew SRO films with various thicknesses d of 5, 15, and 26 nm on STO (001) substrates using a machine-learning-assisted molecular beam epitaxy system. Partial SOT magnetization switching was observed in all films. The chirality of the switching hysteresis loops changes by reversing the sign of the in-plane supporting field applied along the current direction, confirming that SOT drives the observed magnetization switching. The switching current density was in the order of MA cm–2, one order of magnitude smaller than conventional ferromagnet/heavy metal bilayer systems, which highlights the potential of SRO for highly efficient switching. The switching ratio was found to increase in SRO films with larger d. For example, when d = 15 nm, the switching ratio is approximately 3.5 (=11%/3.1%) times larger than when d = 5 nm.