Abstract
Amorphous samples of have been studied by Mössbauer spectroscopy and in some cases by magnetization measurements. The magnetic ordering temperature () decreases sharply with increasing Fe concentration; from 760 K () to 552 K (). The value of of amorphous pure Fe has been extrapolated to about 220 K. Well-defined hyperfine field distributions have been found. The mean hyperfine field is found to be proportional to the average Fe moment with a ratio of about 130 kOe/. The shape of for each alloy is practically independent of temperature. At low temperatures, the effective hyperfine field () shows a temperature dependence of due to spin-wave excitations. The value of increases with Fe concentration. As the Fe concentration is increased in these alloys, the reduced hyperfine field decreases faster with reduced temperature due to a systematic change in the distribution of exchange interactions. A correlation of and the isomer shift exists for crystalline and amorphous Fe-B systems. Crystalline B( K) has been found after crystallizing amorphous samples with under high heating rates. At , B shows at least three magnetically inequivalent sites, whereas at , electric quadrupole interactions are observed. The crystal structure of B is likely to be tetragonal rather than orthorhombic.
- Received 12 January 1979
DOI:https://doi.org/10.1103/PhysRevB.20.283
©1979 American Physical Society