Perpendicular and in plane hole asymmetry in a strained NiFe2O4 film

Strained materials can exhibit drastically modified physical properties in comparison to their fully relaxed analogues. We report on the x ray absorption spectra XAS and magnetic circular dichroism XMCD of a strained NiFe2O4 inverse spinel film grown on a symmetry matched single crystal MgGa2O4 substrate. The Ni XAS spectra exhibit a sizable difference in the white line intensity for measurements with the x ray electric field parallel to the film plane normal incidence vs when the electric field is at an angle off normal . A considerable difference is also observed in the Fe L2,3 XMCD spectrum. Modeling of the XAS and XMCD spectra indicate that the modified energy ordering of the cation 3d states in the strained film leads to a preferential filling of 3d states with out of plane character. In addition, the results point to the utility of x ray spectroscopy in identifying orbital populations even with elliptically polarized x ray