Effect of oxide shells on the magnetic and magnetotransport characteristics of oxidized FeCoZr nanogranules in Al2O3

The paper reports on the results of a comparative study of magnetic and magnetotransport properties of granular nanocomposite films FeCoZr–Al2O3 synthesized in pure Ar and Ar + O sputtering atmosphere. Effects of oxygen incorporation on the temperature and magnetic field dependencies of magnetization and electrical resistance of the films are discussed with respect to the “core–shell” structure formation. Peculiarities of coercive force variation with temperature are analyzed and discussed.

► Sputtering of complex target FeCoZr + Al2O3 in oxygen-containing atmosphere leads to the formation of heterogeneous composite structure containing nanogranules with “FeCoZr core – (Fe3+)Co, (Fe2+)Co oxide shell” in Al2O3 matrix.
► Enhanced coercive force for selected granular films at low temperature is related to the shape anisotropy and/or the pinning effect of spins in the interfaces within the “core–shell” nanogranules.
► Magnetotransport in granular films FeCoZr-Al2O3 with “core–shell” structure follows the mechanism of spin-dependent tunneling above FeCoZr concentration correspondent to percolation threshold.