Exchange bias behaviour in magnetron sputtered Ni49.8Mn36.1Sn13.9 ferromagnetic shape memory alloy thin film

In the present study we report the observation of exchange bias effect in Ni49.8Mn36.1Sn13.9 ferromagnetic shape memory alloy thin film, grown on Si (1 0 0) substrate at 550 °C by dc magnetron sputtering. The shift in hysteresis loop up to 41 Oe from the origin was observed at 5 K when film was cooled under a magnetic field of 2 T. Above 55 K, the exchange bias field disappears and the coercivity gets significantly reduced due to the fact that the pinning between an antiferromagnet and ferromagnet becomes weak with increase in temperature. The observed exchange bias behaviour in Ni49.8Mn36.1Sn13.9 film is attributed to the presence of AFM–FM interactions that result from the coexistence of antiferromagnetic and ferromagnetic phases in the martensite phase of the film at low temperature. This behaviour is an additional property of the Ni–Mn–Sn thin films apart from various other multifunctional properties.

Research highlights▶ Observation of exchange bias effect, for the first time (to the best of our knowledge) in thin film of Ni–Mn–Sn. ▶ Film of a thickness of ∼1 μm was prepared by DC magnetron sputtering and characterized by XRD, EDAX and SQUID. ▶ Shift in hysteresis loop upto 41 Oe from the origin was observed at 5 K when film was cooled under 2 T magnetic field. ▶ Above 55 K, the exchange bias effect disappears and coercivity gets significantly reduced due to the weak pinning between AFM and FM with increasing temperature.