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

Structural transformation, microstructure and magnetocaloric effect (MCE) were investigated in melt-spun Ni55Mn20.6Ga24.4 and Ni55Mn19.6Ga25.4 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 ≈2 K. Maximum entropy changes (ΔSM) of −9.5 and −10.4 J/kg K have been obtained at 309 K for a field change of 2 T in Ni55Mn20.6Ga24.4 and Ni55Mn19.6Ga25.4 ribbons, respectively. The Ni55Mn19.6Ga25.4 ribbon exhibits refrigeration capacity (RC) of 47 J/kg with low average hysteresis loss (≈1.5 J/kg) at the merged structural and magnetic transition temperature.