Enhancement and sign inversion of junction magnetoresistance on Mn substitution in magnetite/p-Si heterostructures

Abstract

Fe3−xMnxO4/p-Si heterostructures (x = 0, 0.25, and 0.5) were prepared using pulse laser deposition to explore their magneto-electric transport characteristics. All the heterostructures exhibit a rectifying property and junction magnetoresistance of 90% (x = 0), 117% (x = 0.25) and 120% (x = 0.5) at room temperature (300 K), low bias voltage (0 to −4 V) and low magnetic field (<1 T). Significantly, the sign (positive or negative) of junction magnetoresistance depends on the range of bias voltage for all heterostructures, but for a particular range of voltage, the sign inversion (positive to negative and vice versa) of junction magnetoresistance is observed in the heterostructure of Mn substituted Fe3O4 (Fe3−xMnxO4) compared to the virgin (Fe3O4) one. The enhancement of junction magnetoresistance and its sign inversion upon Mn substitution in Fe3O4 are assigned to the enhancement of magnetization and the spin filtering at the junction of the heterostructures. The electronic band structure of the Fe3O4/SiO2/p-Si heterostructure and the p-type degenerate semiconducting feature of Mn-substituted Fe3−xMnxO4 films are considered to explain the results.