CEMS INVESTIGATION OF SURFACE HYPERFINE INTERACTIONS IN FE81B13.5SI3.5C2 GLASS

Ferromagnetic amorphous samples of Fe81B13.5Si3.5C2 were exposed isoch ronally to pulsed radio frequency (rf) annealing (v(rf) = 54.8 MHz, ta u(pulse) = 0.1 s) by employing field strengths H-rf which ranged from 3-12 Oe. Conversion electron Mossbauer spectra (CEMS) were analyzed in terms of the rf energy dependence of magnetic hyperfine field (HE;) d istribution. For field strengths H-rf > 6 Oe, CEMS spectra of the rf a nnealed samples showed an additional quadrupole splitting (QS) distrib ution, which was assigned to FeSi clusters. The relative areal intensi ty of the QS distribution, linearly dependent on the rf field energy, is proposed as an appropriate order parameter for the onset of composi tional short-range order (CSRO). An activation energy of 1.7 eV is est imated for the onset of surface CSRO in the rf annealed FeBSiC system.