FMR study of changes in the magnetic behaviour of amorphous Fe<SUB>83-x</SUB>W<SUB>x</SUB>B<SUB>17</SUB> (x = 5,9) alloys due to isothermal annealing. II. In the critical region

Extensive ferromagnetic resonance (FMR) measurements have been performed in the critical region, -0.15 &#8804; &#949;=(T-TC)/TC&#8804;0.15, on amorphous Fe78W5B17 and Fe74W9B17 alloys, before and after they had undergone isothermal annealing treatment at a temperature TA = 400 K for durations of time tA = 1 and 2 h. The values of saturation magnetisation, Ms, and resonance field, Hres, at different temperatures are accurately determined through an elaborate lineshape analysis of the observed FMR spectra. From the Ms(Hres, T) data so obtained, the asymptotic values of the critical exponents &#946; and &#947; for spontaneous magnetisation and initial susceptibility are estimated using the 'range-of-fit' scaling-equation-of-state analysis. Consistent with the predictions of the infinite three-dimensional (3D) ferromagnetic (FM) matrix plus finite spin clusters model and with the well-known Harris criterion, isothermal annealing, which enhances the value of the Curie temperature, TC, considerably, leaves the values of the exponents unaltered from their 'as-quenched' values, which are close to those predicted by 3D nearest-neighbour Heisenberg model. In the critical region, the Gilbert damping parameter and the Lande splitting factor are temperature-independent and structural relaxation has no effect on them