Changes in the electronic structure in superficial space-charge regions may substantially affect the properties of metals near their surface. In materials with a nanoscale porosity and with a high surface to volume ratio, changes in the properties of even a thin surface layer may have a noticeable effect on the properties of the entire material. In nanoporous metals immersed in an electrolyte, the space charge can be induced as a part of the electric double layer at the metal-electrolyte interface. Here we present first experiments on the effect of surface charging in a nanoporous metal on the magnetism. We report reversible changes in the magnetic moment in Ni-Pd alloys. As possible origins of the dependency of the magnetization on the surface charge density we discuss band filling and, alternatively, magnetostriction. X-ray diffraction and dilatometry reveal a considerable strain amplitude, about of 6×10-4, resulting from surface charging; this corresponds to a surface-induced pressure in the crystal lattice, in the order of 0.3 GPa.
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