Structural dependence of the magnetic moment in microcrystalline and amorphous Fe-P alloys

Abstract

The magnetic moment per metal atom in electrodeposited microcrystalline (0 ≤ x ≤ 15) and amorphous ( x ≥ 15) Fe 100- x P x alloys was calculated from the saturation magnetization measured at 4.2 K. Whereas the moment of amorphous Fe-P shows a linear decrease with x, in microcrystalline Fe-P the moment per Fe-atom is independent of the phosphorus content and equals the value of crystalline α-Fe. In contrast to this finding in Co-P the magnetic moment per metal atom decreases linearly with increasing phosphorus concentration without any visible effect at the transition from the microcrystalline to the amorphous structure. This strange behaviour of the microcrystalline Fe-P is quite well described by the coordination bond model, which attributes the constancy of the moment per Fe-atom in bcc-Fe-metalloid alloys to the special coordination symmetry of the bcc-structure. Moreover, our results show that the band-gap theory is totally unsuitable to describe the dependence of the magnetization of Fe-M alloys.