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

초록

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 1.19 & micro;B per Mn and 0.19 & micro;B per Mn, respectively. For the perpendicular orientation under an external magnetic field of 2 T, they are 0.07 & micro;B per Mn and 0.037 & micro;B per Mn, respectively. This results in a similar to 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 Delta R/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.

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