Exchange-bias reversal in Mn2−xNi1+xGa films with antisite disorder

We report on the exchange-bias reversal in Mn2−xNi1+xGa (x = 0, 0.2, 0.4, and 0.6) thin films grown by molecular beam epitaxy on GaAs substrates. Exchange bias reversal is observed in these intrinsically ferrimagnetic films together with a reduction in the total moment even under increasing of Ni content which usually increases the total moment. These magnetic features indicate that antisite disorder is responsible for engender changes in the exchange-bias and total moment. Density functional theory calculations were performed to determine the magnetic moment dependence with the volume of cubic austenite and tetragonal martensite structures. A simple phenomenological approach is used to extract an effective exchange coupling constant from exchange bias fields.