Step-shape angular spin distribution in layered systems by 57Fe Mössbauer spectroscopy: A general treatment

Abstract In the so-called ‘step-shape’ angular spin distribution model for layered systems, the non-collinear directions of the atomic magnetic moments are confined to the film plane and form a homogeneous fan spanning inside an (in-plane) angular interval Δ φ centered at an angle φ 0 . A general approach for deriving the two parameters φ 0 and Δ φ via 57 Fe Mossbauer spectroscopy measurements is discussed. The analysis extends our previously reported treatment, which assumed that the angular aperture Δ φ develops symmetrically versus a fixed direction φ 0 (e.g., the in-plane easy axis of magnetization) oriented either along or perpendicular to the in-plane projection of the Mossbauer γ-ray direction. The proposed approach is also applicable for those cases when not only the spin aperture Δ φ is changing but also the aperture center φ 0 is rotating under the influence of different external parameters, such as applied field, temperature, stress, etc. The method is suitable for applications to nanoscale layered heterostructures with in-plane uniaxial or unidirectional magnetic anisotropy. The method is applied to experimental data obtained on a 2-nm thick defected Fe layer with in-plane magnetic texture.