Spin-polarized tunneling in discontinuous CoFe/HfO2 multilayers

We have investigated the structural, magnetic, and transport properties of discontinuous ${\mathrm{CoFe/HfO}}_2$ multilayers consisting of layers of ferromagnetic particles dispersed in an insulating matrix. Negative magnetoresistance due to spin-polarized tunneling has been observed with the current both in the plane and perpendicular to the plane of the film. The properties of these films are intermediate between tunnel junctions and cermet films. They exhibit high magnetoresistance sensitivity at low fields, are easy to prepare, are very robust due to the protective oxide matrix, and are resistant to electrical breakdown. These properties can be optimized with annealing.