Magnetic properties and surface morphology of Pr-Fe-B thicker films at high annealing temperature

Pr-Fe-B thicker film with the magnetic layer thickness of 500 nm was targeted for investigation of magnetic properties and surface morphology. The film structure of Si ₃N ₄/Pr-Fe-B/Si ₃N ₄ were magnetron sputtered on a preheated glass substrate at a range of temperatures from 500 to 700 °C. The direct effect of annealing temperature on the fixed thickness of magnetic layer resulted in the changes of magnetic properties. The coercivity was found approximately 3.0 kOe at 550 °C and 3.5 kOe at 650 °C. However, the Pr-Fe-B films only showed the potential development of perpendicular magnetic anisotropy at 550 °C. The saturation magnetization exhibited an oscillatory through different temperatures. These magnetic properties were resulted from difference in the magnetic domain structure of the films. The film surface showed a blossom phenomenon with a variability of grain size from 0.05 to 0.5 µm that created the different surface roughness. Microstructures of the thick films at 550 and 650 °C showed the laminated films and formation of new Fe ₃Si phase at the interface of Pr-Fe-B layer/Si ₃N ₄ underlayer. The depth profile of the film at 650 °C confirmed the concentration of two main magnetic elements such as Fe approximately 45 % and Pr approximately 20 % at the interface of Pr-Fe-B/Si ₃N ₄.