Variation of magnetic properties by heat treatment on CoFeNi alloys

In this study, the effect of heat treatment temperature on the magnetic properties and phase of electroplated CoFeNi and CoFeNiCu alloys was investigated. In case of CoFeNi alloys, coercivity, iHc was decreased from 0.4 to 0.2 A/m and permeability was increased from 3.4times10⁶ to 4.6times10⁶ with increasing heat treatment temperature from 100 to 300degC. Saturation induction was increased with increasing heat treatment temperature from 100 to 500 degC. Coercivity of CoNiFe alloy increase rapidly when the heat treatment temperature was higher than 300degC. While, coercivity of CoNiFe alloy increase rapidly when the heat treatment was carried out over 400degC. Increasing heat treatment temperature, bcc and fcc phases in the CoFeNi alloy were grown, bcc phase was precipitated in the CoFeNiCu alloys and then, grain growth was happened.