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

Polycrystalline Fe3O4 films with the thickness of 27 nm were grown at different temperature (T-s) 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 T-s in the range of 500 degrees C - 650 degrees C were proved to be of good crystallization, preferred orientation, and desirable values of saturation magnetization (a little smaller one for film prepared at T-s = 500 degrees C). The lowest density of APBs was verified by the measured bulk like electron-phonon (s-p) coupling constant for film prepared at T-s = 550 degrees C, along with the highest value of spin polarization and the best crystalline quality as the most obvious inflection in the curves of ln rho vs. 1000/T around Verwey transition. This optimum value of T-s can be interpreted by the APBs thermally activated migration process with an activation energy. Films prepared with T-s = 500 degrees C, 600 degrees C, and 650 degrees 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 T-s (T-s = 400 degrees C and 450 degrees C).