[19a-D104-1~11] CS6 10.1 新物質・新機能創成（作製・評価技術）,10.2 スピン基盤技術・萌芽的デバイス技術,10.3 スピンデバイス・磁気メモリ・ストレージ技術のコードシェアセッション

▼ [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)

キーワード：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.