Magnetic investigation of the effect of small additions of Co and Mn on the martensite reversal in Fe-Ni alloys

Data on the temperature, magnetic field, and composition dependency of the magnetic moment and Curie temperature in several Fe-Ni-Co and Fe-Ni-Mn alloys have been obtained. The magnetization/temperature relationship was obtained for each alloy from 298°-873°K, following the change in magnetization through the transformation from martensite to austenite with increasing temperature. The magnetic moment of the alloys was also determined as a function of field at room temperature. The effect of Co and Mn additions to an Fe-30% Ni alloy on the transition temperature A_s the Curie temperature T _c, and the saturation magnetization at absolute zero σ_s0, has been determined. Values for A_s, T _c, and σ₀, the magnetization at absolute zero, were obtained by fitting a Brillouin function to the respective contributions of austenite and martensite to the total magnetization. This technique represents a very sensitive method of obtaining transition temperatures and the respective amounts of each phase present in the alloys. The values of σ₀ were then extrapolated to infinite field to obtain σ_s0. A theoretical prediction of σ_s0 and T_c was in agreement with the experimentally determined values.