Influence of applied tensile and compressive stress on large Barkhausen and Matteucci effects in amorphous wires

Investigation for establishing a residual stress distribution and domain model for amorphous magnetostrictive alloy wires were carried out. Therefore, voltage pulse generation due to the large Barkhausen jump (e
p
) and the Matteucci effect (e
p
') was studied as a function of tensile and compressive stress applied in the axial direction. The wires had a composition of Fe
77.5
Si
7.5
B
15
, made by the in-water quenching technique. The amplitude of the voltage pulses (e
p
and e
p
') and domain nucleation field (H*), are found to decrease smoothly to zero at a critical compressive stress of 5 kg/mm
²
for the as-cast wires. A reduction in the critical stress to 3 kg/mm
²
is observed after altering the wire diameter from 125 to 95 µm by etching. Tensile stress above 20 kg/mm
²
was found to increase e
p
and H*. Squareness ratio (B
r
/B
s
) is observed to be a continous increasing function of applied stress in the range from compressive, zero to tensile stress, being about 0.5 at zero stress. By reducing the diameter by 50% through etching, B
r
/B
s
is found to increase by about 20%. The observed results is indicating a gradually varying residual stress such that the core has a stress induced axial anisotropy and the outer layers has an anisotropy perpendicular to the axis, caused by positive magnetostriction.