Ni-Mn-Ga-Co Ferromagnetic Shape Memory Alloy

This book emphasizes the effects of cobalt, doped selectively for Ni and Mn in the alloy with Ni50Mn29Ga21 as the nominal composition. The effect of Co-doping on the crystal structure, lattice modulation, and microstructural features are discussed. Additional first-order transformations, other than martensitic transformation, are observed in two of the compositions of the Ni-Mn-Ga-Co system. The results indicated that the transformation in Ni46.9Mn28.8Ga21.1Co3.3 is of magnetic origin, while that in Ni49.8Mn27.2Ga21.1Co1.8 is an intermartesitic transformation and is thus of structural origin. Based on the Experimental results, an empirical model was proposed for site preferences of magnetic atoms in the unit cells and the relative orientations of their magnetic moments are discussed.