2012 年 132 巻 10 号 p. 920-923
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.
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