Charge-Dependent Magnetization in Nanoporous Pd-Co Alloys

We explore a concept which promises a reversible change of the magnetic properties of transition metals as the function of an applied voltage, namely introducing space-charge regions at the surface of high surface area metals wetted by an electrolyte. In nanoporous Pd Co alloys near their Curie temperature we find a maximum relative change of about 3% in the magnetization when the electrochemical double-layer is polarized. We discuss this finding with relation to two possible microscopic mechanisms: 1) the filling of the d-band by the extra charge and 2) magnetoelastic response to changes in the surface-induced pressure in the crystal lattice. We suggest that the latter may be the dominant effect.