Direct observation of spin polarization in epitaxial Fe3O4(001)/MgO thin films grown by magnetron sputtering

Abstract

We obtained epitaxial single-crystal Fe3O4(001)/MgO(001) thin films by magnetron sputtering. The high quality of the grown Fe3O4 films was confirmed by reflection high-energy electron diffraction and x-ray photoelectron spectroscopy. Atomic magnetic properties of Fe3O4(001)/MgO(001) were investigated using vibrating sample magnetometry and x-ray magnetic circular dichroism. The values of saturation magnetization and magnetic moment are 407 [Formula: see text] 5 emu/cm3 (3.26 [Formula: see text] 0.04 [Formula: see text]) and 3.31 [Formula: see text] 0.15 [Formula: see text], respectively, in the Fe3O4 film as thin as 5 nm, which are close to the bulk values. The spin polarization was directly measured using spin-resolved photoemission spectroscopy. The measured spin polarization has a maximum value of −42% [Formula: see text] 3%, which is comparable to the theoretical value for the ([Formula: see text] × [Formula: see text])R45° reconstructed Fe3O4(001) surface. Furthermore, the film thickness-dependent measurements indicate that the anti-phase boundaries significantly decrease the spin polarization rather than the lattice mismatch. Our results demonstrate that epitaxial Fe3O4(001)/MgO thin films grown by magnetron sputtering have desired magnetic properties, facilitating the potential application of Fe3O4-based spintronic devices.