Electric-field modulation of perpendicular magnetic anisotropy and damping constant in MgO/Co/Pt trilayers

Electric field modulations of the perpendicular magnetic anisotropy (PMA) and magnetization dynamics of MgO/Co/Pt trilayers were measured by time-resolved magneto-optical Kerr effect (TRMOKE). The anisotropy field estimated from the anomalous Hall effect applying a field along in-plane was confirmed to be modified by the electric field, which results in the PMA variation with electric field of –32 fJ/(V∙m). The PMA variation was also confirmed from TRMOKE measurements, which was estimated to be –47 fJ/(V∙m). From TRMOKE measurements, we also observed the reduction of the inverse of relaxation time 1/τ of the magnetization precession with increasing the electric field. The 1/τ was analyzed by assuming the contributions of effective Gilbert damping αeff, anisotropy distribution, anisotropy angle distribution, and two magnon scattering, and we found αeff decreased with increasing the electric field whose modulation was –0.0046 nm/V, corresponding to –13% per 1 V/nm. These results are similar to the electric field effect in (001)-orientated MgO/CoFeB/Ta trilayers (A. Okada et al., Appl. Phys. Lett. 105, 052415 (2014)), however our finding indicates similar PMA and α modulations are found in MgO/Co/Pt trilayers having MgO(111)/fcc-Co interface.