Effect of Fe substitution by Co on off-stoichiometric Ni-Fe-Co-Mn-Sn Heusler alloy ribbons

We have synthesized Ni45Fe5-XCoXMn40Sn10 Heusler alloy with different Co doping and studied the effect on the structural and magnetic properties of Ni45Fe5-XCoXMn40Sn10 (at. X = 0,2.5,5) ribbons. X-ray diffraction, scanning and transmission electron microscopic characterization reveal the structural/microstructural features in melt-spun ribbons of different compositions. A significant transformation in the crystal structure has been observed in Fe substituted ribbons. The crystal structure changes from cubic L2(1) phase to bi-phasic 4O + L2(1) and 10M + L2(1) modulated phases for the partial and complete substitution of Fe by Co specimens respectively. Williamson-Hall analysis of x-ray diffraction data was used to compute the crystallite size and residual elastic strain. Magnetic properties and magnetic field-induced structural transformation of melt-spun alloy ribbons over a large temperature range of 10 K <= T <= 500 K were examined. Our results revealed that Fe substitution by Co causes a change in the magnetic behavior which could be ascribed to the increase in the lattice strain as well as a magnetic strain due to high antiferromagnetic fraction.