Perpendicular-current giant magnetoresistance of M∕Cu∕M (001) junctions (M=Fe, Co, or Ni): An ab initio study

Abstract

The electronic structure and magnetic properties of semi-infinite Cu(001)∕M∕Cu∕M∕semi-infinite Cu (001) multilayer systems with M=Fe, Co, or Ni have been studied by means of a first-principle Green’s function technique based on the tight-binding linear muffin-tin orbital method. The results show that at the M∕Cu (M=Fe or Co) interfaces there is a net charge transfer from iron and cobalt atoms to the neighboring paramagnetic copper atoms and an enhancement of the iron magnetic moment while at the Ni∕Cu interface, the nickel magnetic moment is reduced compared with its bulk value. This behavior is explained in terms of the relative positions of the Fermi levels of the magnetic material and copper. The conductance is determined in the ballistic limit, in the current-perpendicular-to-the-plane geometry by means of transmission matrix formulation of Kubo-Landauer formalism. It is shown that the oscillations of the giant magnetoresistance ratio are mainly the result of the oscillations of the minority-spin conductance.