Effects of different orientations of Ta underlayer on magnetic properties and microstructures of PR-FE-B thin films

In this study, Si₃N₄(20 nm)/Pr-Fe-B(125 nm)/Ta(50 nm)/glass films were prepared by ultra-high vacuum magnetron sputtering . Ta element is selected as the underlayer material due to it´s high melting point and low chemical activity, which efficiently avoid the interlayer diffusion between Pr-Fe-B and Ta . Besides, different phases of Ta films at various preparation temperatures are the key benefits to study the magnetic properties of PrFeB films without consideration of the large change of surface energy between different element underlayers . Before sputtering, the base pressure of the chamber was about 3×10-7 Torr . 50 nm-thick Ta underlayers were deposited on glass substrate at substrate temperature (TTa) ranging from room temperature (RT) to 700, and following the Pr-Fe-B thin films were sputtered at 650 ⁰C . When the temperature of film was cooled to ambient atmosphere, Pr-Fe-B layer was capped by Si₃N₄ film for oxidation protection . In-plane and out-of-plane magnetic hysteresis loops were measured using a vibrating sample magnetometer (VSM). The microstructure and interfacial behaviors of Ta underlayer and Pr-Fe-B magnetic layer were investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) . Phase structures of the films were analyzed by X-ray diffraction (XRD) .