Magnetization process in NiFe alloys with vanishing anisotropies

The magnetization process in NiFeMo alloys with vanishing anisotropies and variable grain sizes has been investigated through complementary hysteresis loop studies and Barkhausen effect experiments. It is found that the coercive field H∝s^-1 , while the constants a and b of the Rayleigh law I=aH+bH² are proportional to s and s² respectively. Barkhausen noise power spectra show the same shape as in materials with significant anisotropy, i.e. SiFe, even though their amplitudes are two to three orders of magnitude lower. They show a strong dependence on s, approximately decaying as s^-2 at high analysis frequencies. The results, though inconclusive, point to domain-wall motion as an important mechanism in the magnetization process of low-anisotropy NiFe alloys