Magnetic State of Martensite in Ni48Mn39.5Sn12.5-xAlx (x=0,1,2,3) Metamagnetic Shape Memory Alloy Ribbons

P. Czaja The Aleksander Krupkowski Institute of Metallurgy and Materials Science of the Polish Academy of Sciences, 25 Reymonta, 30-059 Kraków, Poland

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Melt spun Ni48Mn39.5Sn12.5-xAlx (x=0,1,2,3) ribbons undergoing a thermoelastic martensitic phase transition concomitant with an abrupt magnetization change were examined with respect to the magnetic response of the low-temperature martensite phase, which shows complex magnetism. It has been shown that in the intermediate temperature range between the martensite finish temperature and the Curie temperature of martensite, the intermediate state is weakly magnetic and is in part composed of a superparamagnetic phase. The average magnetic moment, probed by the modified Langevin model, weakens as the amount of Al increases in the alloys. This might be related to changes in the magnetic response of the parent austenite phase switching from ferromagnetic into paramagnetic, atomic order of which is inherited by the martensite phase. A quasi-magnetic phase diagram was established to trace the evolution of the magnetic response of the ribbons as a function of Al concentration and to aid composition optimisation for engineering applications.

DOI:10.12693/APhysPolA.142.180 topics: shape memory alloy, melt spun, magnetization