Magnetization reversal and hyperfine field in cold-rolled Ni-Fe alloys

The coercive force Hc. saturation magnetization Ms, and squarenessMᵣ/Mₛof cold-rolled binary Ni-Fe alloys were studied at 300°K over the composition range 0 to 100 percent Ni. These alloys were cold-rolled into thin foils with a reduction in thickness higher than 99 percent. In general, HcandMᵣ/Mₛof the Ni-Fe alloys of various compositions showed marked frequency responses when the magnetizaion loops were cycled with fields having very low frequencies varying from 0.02 to 2 Hz. The hyperfine fields in the Ni-Fe alloys at the iron sites were determined by means of the Mössbauer effect. The Mössbauer patterns were used to analyze the magnetic heterogeneities caused by the cold-rolling. As concluded from this work, these heterogeneities seem to become appreciably larger near the Invar composition and may be responsible for the observed peaks in the magnitudes of HcandMᵣ/Mₛof the alloys with 30 and 32.5 percent Ni.