We demonstrate that the proximity-induced exchange field $H_{\mathrm{ex}}$ in ferromagnetic-paramagnetic bilayers can be modulated with an electric field. An electrostatic gate arrangement is used to tune the magnitude of $H_{\mathrm{ex}}$ in the Al component of $\mathrm{EuS}/\mathrm{Al}$ bilayers. In samples with $H_{\mathrm{ex}}\sim 2\mathrm{T}$, we were able to produce modulations of $\pm 10\mathrm{mT}$ with the application of perpendicular electric fields of the order of $\pm {10}^6\mathrm{V}/\mathrm{cm}$. We discuss several possible mechanisms accounting for the electric field’s influence on the interfacial coupling between the Al layer and the ferromagnetic insulator EuS, along with the prospects of producing a superconducting field-effect transistor.

• Received 13 November 2012

DOI:https://doi.org/10.1103/PhysRevLett.111.027207