Structural details and time dependence of the initial susceptibility in iron-rich Fe-Si ribbons

A systematic study of the temperature dependence of the initial susceptibil ity c(AC) versus T of Fe-6.5 wt%Si, Fe-7.5 wt%Si and Fe-11 wt%Si ribbons in the as-quenched state and after annealing at 1373 K for 1 h has been perfo rmed. In ribbons with a silicon concentration of 6.5 and 7.5 wt%, the prese nce of an anomaly in chi(AC) versus T and a thermal susceptibility hysteres is at high temperatures were observed. This susceptibility anomaly is attri buted to the magnetic aftereffect phenomenon originating from the diffusion of pairs of silicon atoms. The occurrence of a magnetic aftereffect is ass ociated with the existence of the B2 type of structure in the sample induce d during the process of cooling from high temperature, its formation being sensitive to the cooling rate. The activation energy of the reversible proc ess of the time dependence of the magnetic susceptibility depends on the co oling rate and its value is estimated using an Arrhenius-type law. X-ray di ffraction and Fe-57 Mossbauer measurements were included within this study, in order to investigate the crystallographic structure. (C) 1999 Published by Elsevier Science B.V. All rights reserved.