Soft Magnetic Properties in Nano-scale Inhomogeneous Ni3Mn Alloys

We have observed superparamagnetic behaviors and giant magnetoresistance in Ni 3 Mn alloy annealed at 673 and 693 K for several periods. The coercive force is small of 0.14 ∼ 0.44 kA.m -1 in these inhomogeneous alloys. The average size of the ferromagnetic cluster increases from ∼2.8 to ∼10nm with long-range ordering. The saturation magnetization also increases with a volume fraction, e, in the ordered regions and reaches to 0.92 T at e ∼ 80% where the alloy is ferromagnetic. These results suggest that the present Ni 3 Mn alloys are magnetically soft due to the nanocrystalline morphology: ordered ferromagnetic domains with nanometer in size are distributed in a disordered nonmagnetic matrix.