Martensitic transformation in Fe42Mn28.3Ga29.7 Heusler alloy accompanied with a huge variation of initial permeability

Abstract

Abstract The martensitic transformation in Fe42Mn28.3Ga29.7 Heusler alloy has been studied using magnetization (M), permeability (μ) and zero-field resistance (R) measurements. The X-ray diffraction profile measured at room temperature indicates that the high-temperature phase of Fe42Mn28.3Ga29.7 alloy exhibits a cubic L12-type crystal structure, with a lattice constant of a = 3.72 ± 0.01 A. Temperature dependence of magnetization showed an unusual increase in the temperature interval from 220 to 340 K, which was attributed to the phase transition. The transition temperatures (TMs - TMf) shift downwards significantly between 340-220 K and 284-57 K under the application of external magnetic fields from 0.05 to 50 kOe. The hysteresis loops showed that the coercivity is drastically reduced from 3800 for the low-temperature phase down to 240 Oe for the high-temperature phase, indicating that the structural transition is accompanied with a transformation from hard to soft magnetic phase. Consequently, the temperature dependence of initial permeability varies by 1700% during the phase transition. The combination of both martensitic transformation and a huge variation in permeability makes such materials ideal for SMART actuator application, where the actuator itself is also used as a sensor.