Effect of ZrO2 layer thickness on microstructure and magnetic properties of FePt/ZrO2 multilayers

FePt (50 nm) and [FePt (x nm)/ZrO2 (0.5, 1, 2, 3 nm)]10 (x = 2, 5 nm) films were prepared by RF magnetron sputtering technique, then were annealed at 550 °C for 30 min. This work investigates the effect of ZrO2 layer thickness on structures and magnetic properties of FePt/ZrO2 multilayers. The X-ray diffraction results show that superlattice (0 0 1) peaks can be found in FePt (50 nm) and [FePt (5 nm)/ZrO2 (0.5, 1, 2, 3 nm)]10 films. Compared with single layer FePt film, superlattice (0 0 1) peaks of FePt/ZrO2 multilayers are wider and weaker, which indicates that introducing ZrO2 is advantageous to hinder the growth of FePt grains. The coercivities, grain size and intergrain interactions of FePt/ZrO2 films are decreased when ZrO2 layer thickness is increased. And grain volume (Vgrain) is almost identical to activation volume (V*) for added-ZrO2 films. Thus, the FePt/ZrO2 films with the appropriate coercivities, the small size of grains, and the weak intergrain interactions are obtained.