Effect of substrate temperature on antiphase boundaries and spin polarization of thin Fe3O4 film on Si (100)

Abstract

Polycrystalline Fe3O4 films with the thickness of 27 nm were grown at different temperature (Ts) on Si (100) substrate by Laser-Molecular Beam Epitaxy to study the influence of density of antiphase boundaries (APBs) and the spin polarization of Fe3O4. Films prepared with Ts in the range of 500 °C - 650 °C were proved to be of good crystallization, preferred orientation, and desirable values of saturation magnetization (a little smaller one for film prepared at Ts = 500 °C). The lowest density of APBs was verified by the measured bulk like electron-phonon (s-p) coupling constant for film prepared at Ts = 550 °C, along with the highest value of spin polarization and the best crystalline quality as the most obvious inflection in the curves of lnρ vs. 1000/T around Verwey transition. This optimum value of Ts can be interpreted by the APBs thermally activated migration process with an activation energy. Films prepared with Ts = 500 °C, 600 °C, and 650 °C still have a reasonable value of the s-p coupling constant compared to recently reported results, while larger magnetoresistance accompanied by the superparamagnetic behavior was observed for films prepared at lower Ts (Ts = 400 °C and 450 °C).