Soft magnetic properties in nano-scale inhomogeneous Ni3Mn alloys

We have observed superparamagnetic behaviors and giant magnetoresistance in Ni3Mn alloy annealed at 673 and 693 K for several periods. The coercive force is small of 0.14 similar to 0.44 kA.m(-1) in these inhomogeneous alloys. The average size of the ferromagnetic cluster increases from similar to2.8 to similar to 10 nm with long-range ordering. The saturation magnetization also increases with a volume fraction, epsilon, in the ordered regions and reaches to 0.92 T at epsilon similar to 80% where the alloy is ferromagnetic. These results suggest that the present Ni3Mn alloys are magnetically soft due to the nanocrystalline morphology: ordered ferromagnetic domains with nanometer in size are distributed in a disordered nonmagnetic matrix.