Spin glass or random anisotropy?: The origin of magnetically glassy behavior in nanostructured GdAl{sub 2}

Initially crystalline GdAl{sub 2} was mechanically milled for long times to produce a highly chemically disordered phase with approximately 8-nm grains. Analysis of dc magnetization measurements using an Arrott plot and the approach to saturation suggest the presence of significant random anisotropy. ac susceptibility measurements showed that the shift in the peak temperature with frequency usually seen in magnetically glassy and superparamagnetic systems was virtually undetectable in the 10-1000-Hz frequency range. Based on these results, we believe that this material represents an interacting system with random anisotropy, where the anisotropy is the result of surface and interface asymmetries.