Mössbauer analysis of spin directions in magnetic recording media: The problem of line area measurements

Interpretations of Mössbauer measurements of the orientation of magnetic moments in magnetic recording particles have recently been critized. It has been alleged that a serious overestimation of spin-canting angles resulted in part from neglecting thick absorber effects. I show that effects are insignificant. The asymmetric and broadened line shapes which occur in Mössbauer spectra of γ-Fe2O3 at room temperature have the consequence that analyses based on line intensities are erroneous, and that line area measurements are inaccurate unless the analysis is performed upon high-quality data and properly accounts for the asymmetry. Cooling γ-Fe2O3 to 4.2 K reduces the line asymmetry and width.