Sequence of structural and magnetic transitions in Ni48Co2Mn39Sn11 shape memory alloy

The structural and magnetic transitions in Ni48Co2Mn39Sn11 shape memory alloy were systematically investigated. During cooling, the paramagnetic austenite transforms into paramagnetic martensite at TM∼375 K, followed by a gradual transition from paramagnetic to superparamagnetic martensite around TS∼320 K. Upon further cooling through TP∼100 K, the superparamagnetic clusters collectively freeze into a superspin glass state as corroborated by aging, rejuvenation, and memory effects. Consequently, the unique transition sequence of paramagnetic austenite→paramagnetic martensite→superparamagnetic martensite→superspin-glass martensite is disclosed.

► We studied the structural and magnetic transitions in the Ni48Co2Mn39Sn11 alloy.
► Paramagnetic austenite transforms into paramagnetic martensite at TM∼375 K.
► A gradual transition from paramagnetic to superparamagnetic martensite is followed.
► Superparamagnetic clusters further freeze into superspin glass state at ∼100 K.
► Finally, the unique transition sequence of this alloy is disclosed.