[19a-D104-1~11] CS6 10.1 & 10.2 & 10.3 Code-sharing session

▼ [19a-D104-2] Bruno mechanism on voltage-controlled magnetic anisotropy in ultrathin cobalt films

〇Takeshi Kawabe¹, Kohei Yoshikawa¹, Masato Tsujikawa^2,3, Takuya Tsukahara¹, Kohei Nawaoka¹, Yoshinori Kotani⁴, Kentaro Toyoki⁴, Minori Goto^1,5, Motohiro Suzuki⁴, Tetsuya Nakamura⁴, Masafumi Shirai^2,3, Yoshishige Suzuki^1,5, Shinji Miwa^1,5 (1.Osaka Univ., 2.Tohoku Univ. RIEC, 3.Tohoku Univ. CSRN, 4.JASRI, 5.Osaka Univ. CSRN)

Keywords:X-ray magnetic circular dichroism, Voltage control magnetic anisotropy, Cobalt

Voltage-controlled magnetic anisotropy (VCMA) in 3d-transition metals such as Fe and Co has been intensively studied. While one mechanism to explain the VCMA is Bruno mechanism, that is, voltage-induced change in orbital magnetic moment in ferromagnetic metals, it has recently been pointed out the significance of the electric quadrupole mechanism to the VCMA in case Pt/MgO interface is employed. However, there has been no report experimentally demonstrating the relative significance between the Bruno and the electric quadrupole mechanisms in 3d-ferromagnetic metals because of a lack of direct observation of the voltage -induced change of orbital magnetic moment in ferromagnetic metals.
We prepared hetero-epitaxial Fe/Co/MgO multilayer. Using in-situ x-ray magnetic circular dichroism spectroscopy, voltage-induced change in orbital magnetic moment of 0.013μ_B was demonstrated in an electric field of ±0.2 V/nm. We find that the VCMA of Co is properly estimated by the induced change in orbital magnetic moment, according to the Bruno mechanism. While we also find the voltage-induced magnetic dipole T_z term induction in Co, the quadruple mechanism only contributed little to the VCMA in 3d-feromagnetic metals.