Manifestation of initial crystallization and c-axis texture in Pr-Fe-B thin films grown on glass substrates

Abstract

Pr2Fe14B-based thin films are the useful nano-material for the high-tech performance of the magnetic devices. With its studied outstanding magnetic property such as high uniaxial magnetocrystalline anisotropy (Ku), high coercivity (Hc), high saturation magnetization (Ms), large energy products (BHmax), excellent anisotropic behavior, and super low spin-reorientation at temperature about 4.2 K, Pr2Fe14B magnetic thin films become an alternative candidate for the Nd2Fe14B-based magnetic thin films. In this study, the perpendicular magnetic anisotropy (PMA) Pr-Fe-B films were deposited on corning glass substrate at 600 °C with Si3N4 cover layer and underlayer from Pr25Fe65B10 alloy target by RF magnetron sputtering technique. VSM, XRD, SEM, TEM, and EDS measurements were applied to investigate the relationship between thickness and the microscopic magnetization structures of the PrFeB layer which initiated and propagated crystallization of PMA Pr2Fe14B phase. The magnetic properties of sputtered Pr-Fe-B film was also investigated in terms of the micro-texture evolution. The structure with thickness 50 nm showed the initial point of crystalline characteristic. The initial appearance signal of c-axis orientation of Pr2Fe14B phase and the perpendicular coercive force in the film were comparable at 50 nm, and were alternatively evolved on glass substrates. SEM, TEM, and EDS results revealed that localized grains occurred at the initial stages of growth, and developed non-uniform grain networks across the substrate. The highly c-axis oriented films have a special microstructure which Pr2Fe14B phase showed blossom surface morphology. The exchange coupling was mainly explained for the two-phase nanostructure formed from hard magnetic phase and soft magnetic phase. The texture with the c-axis perpendicular to the film plane had finely signal of development after in-situ annealing at 600 °C. The magnetization irregularity of the thin film was strongly affected by the underlayer and the substrate. The magnetic analysis assuming that the value of film was composed of the correlation between microstructures and magnetic properties on underlayer and substrates.