We present measurements of the small-field magnetic response of non-or
iented 1.8 wt% SiFe and rapidly-quenched 6.5 wt% SiFe as a function of
various magnetic histories. The first part of the return branch origi
nating from a given turning point (H-0,B-0) was fitted by the quadrati
c law B - B-0 = mu(rev) (H - H-0) +/- (b/2) (H - H-0)(2) and the depen
dence of mu(rev) and b on (H-0,B-0) and magnetic history was studied.
mu(rev) and b approximately follow the laws mu(rev) proportional to [1
- (B-0/B-m,)(2)] + const, b proportional to [1 - \B-0/B-m\], mu(rev)
proportional to exp[:H-0(2)/2 sigma(mu)(2) r2]+ const, and b proportio
nal to exp[-H-0(2)/2 sigma(b)(2)].