Nearly compensated ferrimagnetic behaviour and giant exchange bias of hexagonal MnPtAl: experimental and theoretical studies

We have investigated the Mn 2 PtAl Heulser alloy to unravel its structural, magnetic, calorimetric and electronic structure properties. At room temperature, the alloy crystallizes in a hexagonal structure. Magnetization reveals a weak martensitic transition at 307 K, followed by a long range ferrimagnetic transition at 90 K. Griffiths phase-like signature and positive Weiss temperature in dc-magnetization, isothermal magnetic hysteresis loops and a frequency-independent peak confirm a nearly compensated ferrimagnetic order of Mn 2 PtAl. The theoretical electronic structure calculations also reveal the ferrimagnetic ground state of Mn 2 PtAl and Mn ions (occupying different sites) with a very small total magnetic moment. A giant exchange bias field of 2.73 kOe, at a temperature of 3 K and a cooling field of 70 kOe, has been estimated and is attributed to the unidirectional anisotropy associated with possible ferromagnetic clusters formed by the field cooling process in the ferrimagnetic matrix. We have investigated the Mn 2 PtAl Heulser alloy to unravel its structural, magnetic, calorimetric and electronic structure properties.