Magnetic behavior in Ni–Fe–Ga martensitic phase

The magnetic behavior of a polycrystalline Ni53.5Fe19.5Ga27 (at.%) alloy in the low-temperature martensitic phase has been analyzed. The alloy undergoes a martensitic transformation (MT) below room temperature from austenite to a mixture of five (10M) and seven (14M) layered phases. The order degree of the alloy modifies not only some characteristics of the MT but also the magnetic behavior in the martensite phase temperature range. The real component of the AC magnetic susceptibility displays a broad peak in that region that shifts towards higher temperatures as disorder increases. The peak disappears under application of a 500 Oe bias field. In turn, the DC magnetization curves under different applied constant fields in the range of 0–500 Oe show similar maxima at corresponding temperatures, while for higher magnetic fields the peak disappears. No discontinuities in the saturation magnetization (measured at 6 T) have been observed in this martensitic region. Structural changes such as modifications in the volume fraction of martensitic phases seem to be involved in the magnetic behavior of the alloy below the MT.