Effect of Buffer Layer Annealing on the Growth of (001)-Textured MnGa Ultrathin Films With Perpendicular Magnetic Anisotropy

The effect of buffer layer annealing on the growth of (001)-textured 3 nm thick MnGa films with perpendicular magnetic anisotropy (PMA) was investigated. The film stacking of Si/SiO₂ substrate/MgO/Cr/CoGa/MnGa was fabricated by magnetron sputtering. It was found that the CoGa buffer layer crystallized with a (001) orientation and B2 chemical ordering even without any thermal treatments. Interestingly, the 3 nm thick MnGa grown on the un-annealed CoGa buffer layer showed PMA, indicating that the CoGa buffer layer promoted the growth of (001)-textured MnGa films with L1₀ chemical ordering even without the annealing process. Annealing the CoGa buffer layer above 400 °C improved the (001) orientation of the CoGa buffer and MnGa layers. The effective PMA constant K_u^eff was about 4 Merg/cm³ without the annealing and was slightly reduced with increasing the annealing temperature, whereas the PMA dispersion was improved by the annealing. These results can help to obtain (001)-oriented MnGa ultrathin films with high PMA.