Magnetic hyperfine interactions in amorphousFexB100−x

Abstract

Sputtered amorphous ${\mathrm{Fe}}_x{\mathrm{B}}_{100-x}$ has been studied by ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ Mössbauer spectroscopy from below the magnetic threshold at $x_c\simeq 38$ through the magnetic region, to $x=90\mathrm{}$. $T_C$ is found to rise sharply with Fe concentration, peaking at $x\simeq 70$, and then to decrease monotonically. Measurements under a small external field indicate that these samples are ferromagnetic. The hyperfine field distributions $\mathrm{}\left\{P\right(H\left)\right\}$ exhibit rather structureless, single-maximum patterns that continuously shift to higher $H$ values as the Fe concentration is increased. The isomer shift, on the other hand, shows a maximum at $x\simeq 50$. The data are discussed in terms of the localized moment and itinerant electron descriptions. It is also shown that several models (e.g., charge-transfer and quasicrystalline models) based on the results from liquid-quench samples with $72\le x\le 86$, are not valid over the wider composition range studied here. The magnetic properties and hyperfine interactions of sputtered and liquid-quench samples are compared in the region of common compositions.