Effect of Co and Ni doping on the structure, magnetic and magnetocaloric properties of Fe-rich (Mn,Fe)2(P,Si) compounds

Abstract

The effect of Co and Ni doping on the structure, magnetic and magnetocaloric properties of Fe-rich (Mn,Fe)2(P,Si) compounds was studied. With increasing Co and Ni content, both the Curie temperature (Tc) and the thermal hysteresis (ΔThys) decreased, whereas the hexagonal P-62 m crystal structure was maintained. A pronounced reduction in hysteresis was observed upon Co doping, while a significant reduction in Curie temperature was found upon Ni doping. Mössbauer spectroscopy measurements and DFT calculations indicated the substitution of Fe at the 3f site for both Co and Ni doping. Rietveld refinement of the X-ray diffraction data showed that Co substitute atoms in the main phase and the impurity phase, while Ni exhibits an affinity to the main phase. Magnetization measurements on the Co doped samples revealed an increase in magnetization for 2 at.% of Co, followed by a decrease for higher concentrations. DFT calculations showed that the magnetic moment on the 3f site is enhanced by Co substitution, whereas an opposite trend was observed for Ni substitution.