An electric field applied to a ferromagnetic metal produces a surface magnetoelectric effect originating from the spin-dependent screening of the electric field which results in a change in the surface magnetization of the ferromagnet. Here we predict that if the ferromagnet is a half-metal, due to the screening charge formed solely by single-spin conducting states, the surface magnetoelectric coefficient is the universal constant ${\mu }_B/e{c}^2\approx 6.44\times {10}^{-14}\text{G}{\text{cm}}^2/\text{V}$. This prediction is in excellent agreement with results of our first-principles calculations of the magnetic response of a half-metallic ${\text{CrO}}_2$ to an applied electric field. The universal value of the surface magnetoelectric coefficient in half-metals may be used as another tool for detecting half-metallicity.

• Received 3 March 2009

DOI:https://doi.org/10.1103/PhysRevB.79.140403