Magnetic and structural properties of Mn-Ga thin films

A systematic experimental work has been conducted to understand the magnetic properties of Mn-Ga thin films. Multilayer structured thin films of [MnGa 2 nm/Mn x nm]×25 (x = 0.2∼3.5, which corresponds to Mn at%56∼86) were sputter-deposited onto silica glass substrates, followed by annealing in vacuum. It is found that the magnetic properties strongly depend on x. For x = 0.5, the high magnetization values are found, where the nanocrystalline L10 structure is present. The samples with x = 2.0-3.0 exhibit the coercivity Hc higher than 10 kOe at room temperature where the nanocrystalline D022 structures are found to form. The correlation between the magnetic anisotropy constant K and saturation magnetization Ms is also discussed. The nth power dependence of magnetic anisotropy constant K on Ms is found, where the values of n are 7.8 and 1.9 for x = 0.5 and 2.5, respectively. The present result of the power dependence of n equals about 8 for the L10 MnGa suggests that the magnetic anisotropy in a nanocrystalline L10 MnGa phase is much different from the ordered FePt phase. On the other hand, the power dependence of the D022 nanocrystalline phase suggests the two-ion mechanism.