J. M. Rondinelli, M. Stengel and N. A. Spaldin, Nature Nanotechnology 3, 46 (2008)

The search for a general means to control the coupling between electricity and magnetism has intrigued scientists since Ørsted's discovery of electromagnetism in the early 19^th century. While tremendous success has been achieved in creating both single phase and composite magnetoelectric materials, the quintessential electric-field switching of magnetism remains a challenge. In this work we demonstrated a  linear magnetoelectric effect which arises from a carrier-mediated mechanism, and is a universal feature of the interface between a dielectric and a spin-polarized metal. Using first-principles density functional calculations, we illustrated this effect at the SrRuO₃/SrTiO₃ interface and describe its origin. To formally quantify the magnetic response of such an interface to an applied electric field, we introduced and defined the concept of spin capacitance. In addition to its magnetoelectric and spin capacitive behavior, the interface displays a spatial coexistence of magnetism and dielectric polarization suggesting a route to a new type of interfacial multiferroic.