The magnetic domain and properties of amorphous ribbons

The magnetic behavior of Fe
78
B
13
Si
9
amorphous ribbons has been investigated by means of observations of the magnetic domains and measurements of the magnetization curves and core losses. The Fe
78
B
13
Si
9
samples, which were 10 mm wide and approximately 25 μm thick, were annealed under 10
^-3
torr, from 200°C to 425°C, in a dc magnetic field of 1600 A/m directed along the ribbon length. The magnetic domains formed simple 180° patterns parallel to the ribbon length, and the ribbons showed the best quality magnetic properties after magnetic field annealing at 350°C. After annealing below this temperature, the domain patterns and magnetic properties of the samples were similar to those of the as-cast ribbons. In contrast, after a magnetic field annealing above 400°C, the domain patterns distorted, and the magnetic properties deteriorated. The resultant air-pockets and holes on the surfaces of the amorphous ribbons trapped the magnetic domains and caused distorted domain patterns. In the stress pattern observed on the convex side of a bent amorphous ribbon, the domain width narrowed as the bending radius was increased.