Microstructure, magnetic properties and magnetocaloric effect in melt-spun Ni-Mn-Ga ribbons

摘要

Structural transformation, microstructure and magnetocaloric effect (MCE) were investigated in melt-spun Ni_(55)Mn_(20.6)Ga_(24.4) and Ni_(55)Mn_(19.6)Ga_(25.4) ribbons. Magnetic and thermal studies of the ribbons revealed the occurrence of simultaneous structural and magnetic transitions near room temperature with a narrow thermal hysteresis of magnetization approx =2K. Maximum entropy changes (DELTA S_M) of -9.5 and -10.4J/kgK have been obtained at 309 K for a field change of 2T in Ni_(55)Mn_(20.6)Ga_(24.4)and Ni_(55)Mn_(19.6)Ga_(25.4)ribbons, respectively. The Ni_(55)Mn_(19.6)Ga_(25.4) ribbon exhibits refrigeration capacity (RC) of 47J/kg with low average hysteresis loss (approx =1.5J/kg) at the merged structural and magnetic transition temperature.