ROOM-TEMPERATURE PERMINVAR EFFECT AND WIDE DOMAIN-WALLS IN NEARLY-ZERO MAGNETOSTRICTIVE AMORPHOUS RIBBONS

The low-field ac complex susceptibility chi* of as-quenched melt-spun amorphous ribbons with nearly-zero magnetostriction lambda(s) has been measured as a function of the field amplitude H(m) and frequency f. It has been found that there is a jump on the chi* versus H(m) curve at H(m) almost-equal-to 2 A/m. Before the jump, chi* is constant. This is a room-temperature Perminvar phenomenon, due to domain wall pinning by local induced anisotropy. The constant susceptibility is dominated by domain magnetization rotations, while the jump is ascribed to domain wall depinning. Using a new eddy-current losses model together with relaxation analysis, it is further deduced that only very few wide (around 4-mu-m) walls exist in such ribbons.