Effect of Annealing Temperature on the Microstructure and Magnetic Properties of MnGa Films

Abstract

MnGa films are the promising magnetic recording materials and spintronic materials owing to their intrinsic properties, such as large magnetic anisotropy, high coercivity, moderate magnetization, and high spin polarization. In this paper, MnGa films with high coercivity and low surface roughness have been successfully fabricated onto MgO substrates by magnetron sputtering and post-annealing. Moreover, the effects of post-annealing temperature (T a) on crystalline structure, surface morphology, and magnetic performances of MnGa films have also been investigated. It is found that the crystallization temperature for MnGa films is 400 ∘C. With increasing T a, the crystallization degree enhances and an in-plane texture is formed. The grain size and surface roughness of MnGa films increase slowly when T a is below 500 ∘C, but they exhibit a rapid rise when T a is above 500 ∘C. As T a increases, the coercivity (H c) and remanence squareness ratio (S) for MnGa films improve monotonically, whereas saturation magnetization (M s) increases firstly and then drops. The increases in H c, S, and M s with T a are attributed to the grains’ growth and the improvement of crystallinity, and the decrease of M s at higher T a possibly is due to the partial oxidation of Mn.