Observation of a large magnetocaloric effect and suppressed transition in Ti doped Ni-Co-Mn-Sn ribbons upon annealing

We report the presence of austenite and its magnetostructural transition to martensite resulting in a large magnetocaloric effect in Ti doped Ni-Co-Mn-Sn textured ribbons. The evolution of the microstructure, micro-texture and the dynamics of the magnetostructural transition were studied for the as-spun and annealed Ni41.5Ti0.5Co9Mn39Sn10 ribbons. The as-spun ribbons revealed the evolution of a cubic superstructure of B2 ordering at room temperature, which is the characteristic of the austenite phase. The as-spun ribbons possess a strong preferred orientation at room temperature wherein, the < 100 > parallel to ND fiber texture is the dominant contribution at 90.2%. The austenite is ferromagnetic in nature and undergoes a magnetostructural transformation to weak magnetic martensite at 283.4 K. A large value of the isothermal entropy change of 6.62 J/kg/K, relative cooling power of 114.52 J/kg and an adiabatic temperature change of - 2.6 K have been calculated for a relatively low magnetic field change of 2 T. The annealing and quenching of the ribbons led to the grain growth as well as an overall suppression of the magnetostructural transformation. The austenite phase showed an overall enhancement in its magnetization when field cooled down to low temperatures of 4 K. The presence of strain glass clusters generated in the B2 lattice during the quenching process could be accounted for the observed behavior. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

The presence of austenite and its magnetostructural transition to martensite in Ti doped Ni-Co-Mn-Sn textured ribbons is reported, leading to a large magnetocaloric effect at room temperature. The as-spun ribbons exhibit significant isothermal entropy change, relative cooling power, and adiabatic temperature change even with a relatively low magnetic field change of 2 T.