Thickness dependence of magnetic and magnetotransport properties of textured Fe3O4 ferrimagnetic films on SiO2/n-Si(001)

Abstract

The efficient injection of spin-polarized charge carriers from a ferro- or ferrimagnet into a semiconductor is an urgent problem. Half-metal magnetite (Fe3O4) is an attractive candidate for the role of a spin injector in spintronic devices. Here, the influence of the thickness of magnetite films on their electrical, magnetic, and magnetotransport properties is presented. Polycrystalline magnetite films with (311)-texture and thickness ranging from 15 to 250 nm are grown on the oxidized silicon surface by reactive iron deposition in the molecular oxygen atmosphere. The saturation magnetization is found to increase nonmonotonically with the film thickness and reaches its maximum value at 170 nm, which is close to that of a single crystal (∼480 emu/cm3). It is shown that for films with a thickness of more than 150 nm, there is a rapid decrease in resistivity by almost three times. The critical film thickness at which the coercive force decreases to the lowest value of ∼250 Oe is 100 nm. The magnetoresistance value reaches − 2.5 % already at a thickness of 50 nm and remains almost unchanged with a subsequent increase in the thickness of the textured film. Since, at a small thickness, textured films have higher magnitudes of conductivity and magnetization than conventional polycrystalline films, the textured-F3O4/SiO2/n-Si(001) junction with amorphous SiO2 barrier is promising for Si-based spintronic devices.