Potential explanation of charge response of magnetization in nanoporous systems

Abstract

An example of technologically promising magnetoelectric effects in nanostructures is the reversible tuning of the magnetic properties of nanoporous systems by charging them in an electrolyte. So far this effect, which has been observed experimentally in various metallic nanoporous materials, has been tentatively related to two different microscopic mechanisms: the filling of the electronic $d$ band upon charging, or the magnetoelastic response to charge-induced structural changes of the nanoparticles which form the nanoporous systems. In the present paper a potential mechanism is introduced which is related to a change in the magnetic surface anisotropy of the nanoparticle upon charging. An essential assumption of the mechanism is that only those surfaces of the nanoparticle which are not in the grain-boundary contact with the neighboring nanoparticles of the nanoporous material are charged in the electrolyte. This is underpinned by computer simulations on the atomic level with information on the charge response of the magnetic surface anisotropy from ab initio electron density functional calculations.