La-Zn substituted hexagonal Sr ferrite thin films for high density magnetic recording

La-Zn substituted M type Sr-ferrite thin films were prepared by conventiona l rf diode sputtering. The crystallography, surface morphology, magnetic pr operties, and their temperature dependence were investigated by x-ray diffr actometry, atomic force microscopy, and vibrating sample magnetometry. La-Z n substitution reduces the grain growth rate, so that it was possible to ob tain fine grains with mean grain size about 12 nmx12 nm. Suitable amount of La-Zn substitution increases the saturation magnetization M-s of the films without changing the magnetocrystalline anisotropy of the material. As a r esult, the coercivity H-c increases with the increase of the La-Zn substitu tion. La-Zn substitution also reduces the values of dH(c)/dT of the films i n the vicinity of room temperature. (C) 2000 American Institute of Physics. [S0021-8979(00)05905-3].