Heat treatment effect on magnetic properties in rapidly solidified Co-Fe alloy

In this study, heat treatment effect on the rapidly solidified Co-Fe alloys with high Co content was investigated for synthesizing a compact magnetic sensor with high-performance. The Co-Fe alloy ribbons with 71 and 75 at% Co and with 70 nm in the thickness were produced by a single Cu-roller rapid solidification, and subsequently heat treatment was conducted. For evaluation of the heat treatment effect, magnetic properties such as magnetization, coercivity, magnetostriction and susceptibility were measured as well as crystal structure. The saturation magnetization and saturation magnetostriction for the Co₇₅Fe₂₅ ribbon annealed at 750°C exhibited no remarkable change without any relation to the annealing time. On the other hand the Co₇₅Fe₂₅ alloy ribbon revealed annealing time dependency of both magnetization and magnetostriction, it was found that the short time annealing is effective in increasing the saturation magnetostriction. Maximal saturation magnetostriction of the Co₇₅Fe₂₅ alloy ribbon annealed at 750°C reached to 96 ppm, 33% higher than that of the Co₇₁Fe₂₉ alloy. As a result magnetostrictive susceptibility for the annealed Co₇₅Fe₂₅ alloy ribbon became higher than that of the annealed Co₇₅Fe₂₅ alloy ribbon and it is considered that the optimal annealing Co₇₅Fe₂₅ alloy ribbon has excellent functionalities as an element material of the magnetic sensor.