In-plane and perpendicular exchange bias effect induced by an antiferromagnetic D019 Mn2FeGa thin film

Fe-doped D019 Mn3Ga films were studied in terms of both their in-plane and perpendicular exchange bias field, Hex, induced in the attached ferromagnetic layer. The (Mn,Fe)3Ga films were deposited on a Si substrate with a Ru buffer layer with a (0001)-oriented single D019 phase at room temperature. Consequently, in-plane and perpendicular Hex were measured in bilayers with a CoFe layer and a [Co/Pt] multilayer, respectively. In-plane Hex was found to be dependent on the Fe compositions, showing the largest value of 446 Oe at 120 K for 10-nm-thick Mn1.99Fe0.41Ga. Perpendicular Hex was dependent on not only the Fe compositions but also the thickness of (Mn,Fe)3Ga, exhibiting the maximum of 163 Oe at 120 K for 5-nm-thick Mn1.96Fe0.67Ga . The median blocking temperature of both in-plane and perpendicular Hex systems for 10-nm-thick (Mn,Fe)3Ga were measured to be 235 and 240 K, respectively. The measured in-plane and perpendicular Hex induced by (Mn,Fe)3Ga are generated by a spin structural change from noncollinear to noncoplaner in ab-plane as expected from the previous theoretical study [A. Kundu and S. Ghosh, Intermetallics 93, 209 (2018)].