Orbital-dependent electric field effect on magnetism in ultrathin cobalt

摘要

Electric field modulations of magnetism in ferromagnetic metals are in general ascribed to the electric field effects on the orbitals. However, a direct observation of the electric-field-induced changes in the orbital states of a ferromagnetic metal is lacking. In this Rapid Communication, we demonstrate that an electric field applied to an ultrathin Co film can change the electron occupations according to the orbitals, combining x-ray absorption and x-ray magnetic circularly dichroism spectroscopies with the sum rules. Under a positive electric field, the d_(xz(yz))-occupied states decrease mainly via the modification of orbital hybridizations, while the d_(z2)-occupied state increases. The changes in the d_(xz) and d_(yz) states dominantly alter the Curie temperature.