Non-collinear Magnetic Structure on the Fe3O4(111) Surface

The magnetic structure of an Fe3O4(111) surface was observed at room temperature by nuclear resonant X-ray scattering (NRS) and conversion electron Mössbauer spectroscopy (CEMS). The depth dependence of the magnetic structure was investigated by using natural and 57Fe3O4-deposited Fe3O4(111) surfaces. The CEMS results showed that the magnetization direction of the near-surface regionis close to the non-perpendicular easy-magnetization axes. The NRS results showed that the (111) surface includes in-plane magnetization components, suggesting that the surface contains domains that are magnetized along non-perpendicular directions. These results are consistent with the idea that the surface is covered with closure domains with magnetization along the non-perpendicular easy-magnetization directions. It was also found that, near the surface, the spin direction of the Fe(B) site is more parallel to the surface than the non-perpendicular easy axes while that of the Fe(A) site corresponds to the easy axes. This indicates that the spins of the Fe(A) and Fe(B) sites are non-collinear in the near-surface region. The thickness of this Fe(B) canting layer is estimated to be larger than the probing depth of CEMS (45–60 nm).