Anomalous Relaxation in Magnetoresistance of Fe/Fe-O Granular System

Abstract

Fe/Fe-O granular thin films were fabricated by gas flow sputtering. Transmission electron microscopy analysis reveals that α-Fe granules are surrounded by a matrix consisting of tiny crystallites of Fe₃O₄ and/or γ-Fe₂O₃. The matrix acts as a tunnel barrier for electrical conductance. The Fe/Fe-O granular thin film exhibits an anomalous response to magnetic fields at low temperatures. When a magnetic field is applied, the resistance decreases. After the field is settled, the resistance increases for more than 1800s. A possible mechanism for the anomalous relaxation is the relaxation of the spins in the spin-glass-like Fe-O matrix.