Control of the perpendicular magnetic anisotropy and microstructure of L1₀-CoPt/TiN multilayer films with the TiN layer on glass substrates

TiN(5 nm)[CoPt(4 nm)/TiN(x nm)]₅ multilayer films (x = 1, 2, 4, 6, 8, 10, 14) have been deposited on glass substrates by dc magnetron sputtering, and a L1₀-CoPt structure with perpendicular magnetic anisotropy (PMA) has been obtained after annealing at 700 and 800°C. It is found that changing the TiN layer thickness and annealing temperature significantly affects the ordering degree and magnetic anisotropy energy of L1₀-CoPt/TiN multilayer films. To obtain the maximum value of the ordering degree and magnetic anisotropy energy, the optimum thickness of the TiN layer is around 4 and 8 nm, with an annealing temperature of 700 and 800°C, respectively. Structural characterization results have shown that the thickness of the TiN layer greatly affects the interface structure between CoPt and TiN layers. When TiN layer thickness is below 2 nm, it tends to be discontinuous after annealing, which results in the coalescence of the adjacent CoPt layers. When TiN layer thickness is above 8 nm, the interface roughness becomes larger. In such cases, the preferred orientation, ordering degree of the L1₀ structure and the PMA of the films will be impaired.