Giant strain-induced magnetic anisotropy in the skyrmionic-textured MnSi thin films via polarization-dependent X-ray magnetic circular dichroism and X-ray near-edge spectroscopy.

We investigated the tensile strain-induced in-plane magnetic anisotropy in (400)-textured polycrystalline MnSi thin films grown on c-Al2O3 substrates using angle-dependent Mn L2,3-edge X-ray absorption spectroscopy (XAS), X-ray magnetic circular dichroism (XMCD) and extended X-ray absorption fine structure (EXAFS). We observed a 17-fold increase in the in-plane spin magnetic moment and a 413.5% increase in the orbital magnetic moment compared to the out-of-plane direction. The spin and orbital magnetic moments measured parallel to the film plane are 1.19µB per Mn and 0.19µB per Mn, respectively. For the perpendicular orientation under an external magnetic field of 2 T, they are 0.07µB per Mn and 0.037µB per Mn, respectively. This results in a ∼30% reduction in the effective spin-sum rule error due to the presence of the mixed-valence ground-state configuration |Mn3d7/Si3p2〉 + |Mn3d6/Si3p3〉 in the MnSi thin film. This is consistent with cluster-model calculations. The substantial decrease in morb/mspin in the in-plane direction compared to the out-of-plane direction, along with the applied magnetism, indicates a finite enhancement of the spin moment in the in-plane direction of the film. This enhancement arises from weak ligand-metal (p-d) hybridization between Si 3s-3p and Mn 3d orbitals and significantly strong on-site Mn d-d Coulomb interactions. The non-zero ΔR/R values extracted from the polarization-dependent EXAFS suggest the presence of different degrees of in-plane and out-of-plane substrate-induced strain in the MnSi thin film. The co-existence of partially localized and itinerant Mn 3d states plays a crucial role in stabilizing this strain-induced magnetic anisotropy in the MnSi thin films.