Magnetocaloric behaviour of crystalline NiMnGa based alloys and amorphous (Fe, Co)SiB alloys
ABSTRACT :
In recent years, magnetic refrigeration technology has gained importance over the issues related to maintenance and the hazardous effect of gas compression-expansion methodologies. Magnetic refrigeration is based on the phenomenon of magnetocaloric effect and is characterized by isothermal magnetic entropy change and working temperature span of the magnetic material. The simultaneous optimization of isothermal magnetic entropy change and working temperature span remains an open challenge. The present investigation addresses tailoring of magnetostuctural coupling and modification of martensite phase in Ni-Mn-Ga based alloy system. Efforts are made to synthesize new materials and also to explore new processing routes like melt-spinning and optimal heat treatment to expand the working temperature span. A comparative study of magnetocaloric behaviour in rapidly solidified ribbons and its bulk has been carried out. Structure-property relationships in Ni-Mn-Ga based alloys have been established. The magnetocaloric properties of rapidly quenched FeSiB and CoSiB monolayer and bilayer ribbons will also be discussed.