Understanding the magnetic anisotropy in Fe-Si amorphous alloys

The origin of the magnetic anisotropy in a very disordered Fe-Si alloy has been investigated. The alloy containing 40% at. Si was prepared in the form of a thin film in a dc magnetron sputtering chamber. Structural disorder was obtained from extended X-ray absorption fine structure spectroscopy. The uniformity and lack of inhomogeneities at a microscopic level was checked by measuring their transverse magnetic susceptibility and hysteresis loops. The orbital component of the magnetic moment was measured by X-ray magnetic circular dichroism spectroscopy. The orbital moment was extraordinary high, 0.4 μ_B. Such a high value contrasted with the relatively small uniaxial anisotropy energy of the thin film (2 kJ/m³). This suggests that the cause of the magnetic anisotropy in this alloy was a small degree of correlation in the orientation of the local orbital moments along a preferential direction.