Effect of annealing temperature on characteristics of Ni 49Fe 51 films sputter deposited on SiO 2/Si (1 0 0)

Abstract

240 nm-thick Ni 49Fe 51 films were sputter deposited on SiO 2/Si(1 0 0) substrates at room temperature and then annealed in vacuum at 300, 400 and 480 °C for 1 h, respectively. Structural, electrical and magnetic properties of the films were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), four-point probe technique and a vibrating sample magnetometer(VSM). The as-deposited film grows with crystalline orientations of [1 1 1], [2 0 0] and [2 2 0] in the direction of the film growth. The [2 2 0] orientation of the film increases markedly with increasing annealing temperature. The as-deposited film grows with thin columnar grains and has void networks in the grain boundaries. The grain size increases gradually and the void networks decrease with increasing annealing temperature. Furthermore, the void networks shorten and widen with annealing temperature. The resistivity of the film decreases and the saturation magnetization of the film increases with annealing temperature. The as-deposited film shows a hard magnetization requiring a saturation field of 1.43×10 5 A/m. As the annealing temperature increases, the film becomes gradually an easy magnetization. The coercivity of the film annealed at 480 °C is 9.07×10 3 A/m. The as-deposited and annealed films have an isotropic magnetization characteristic.