Anisotropic magnetostriction of an amorphous itinerant magnetY2Feand a simple random crystal-field model

Abstract

The anisotropic magnetostriction ${\ensuremath{\lambda}}_{t}$ and the magnetization are measured for the amorphous ${\mathrm{Y}}_{2}\mathrm{Fe}$ intermetallic compound in the temperature range 3--300 K, in magnetic fields up to 9 T. The low-field ac (1 Hz) susceptibility shows a cusp at ${T}_{\mathrm{SG}}=3\mathrm{K}$ typical of spin-glass freezing. At 3 K and 9 T the magnetic moment of iron atoms is as small as $0.175{\ensuremath{\mu}}_{B},$ but the magnetostriction is found to be ${\ensuremath{\lambda}}_{t}\ensuremath{\cong}16\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}.$ The magnetostriction results are interpreted within a random-crystal electric-field (RCEF) model, which is a simplified band version of the random anisotropy model for localized magnetic moments. Good agreement is found between the thermal dependence of ${\ensuremath{\lambda}}_{t}$ (9 T) and the model calculation, showing that $a\ensuremath{-}{\mathrm{Y}}_{2}\mathrm{Fe}$ is a spin glass but of random magnetic anisotropy origin (speromagnet). The model shows an enhancement of ${\ensuremath{\lambda}}_{t}$ by the RCEF near the band electron filling, with ${\ensuremath{\lambda}}_{t}$ peaking at the model RCEF parameter value.