Nd–Fe–B Thin Films with Perpendicular Magnetic Anisotropy and High Coercivity Prepared by Pulsed Laser Annealing

Abstract

Amorphous, as-deposited Nd–Fe–B films prepared by RF-sputtering were annealed by irradiating pulsed KrF excimer laser (248 nm). A pulse of 20 ns in width and 4 kJ/m2 in power density was irradiated onto a 2 µm-thick as-deposited film kept at 400°C. It is observed that, by a single shot of the pulse, Nd2Fe14B Φ phase crystallized with prominent texturing of c-axis along the film normal. Annealed films showed excellent magnetic characteristics; Ms=0.978 T, Mr=0.906 T, iHc=1272 kA/m, and (BH)MAX=161 kJ/m3. This process is also found to be successfully applicable to a 20 µm-thick film. Using 2 µm-thick as-deposited film kept at 400°C, micro-magnet patterns of 100 µm in width and 1–2 mm in length were fabricated by irradiating a 20-ns pulse shot through a patterned mask. The patterned area revealed that magnetizations are directed along the film normal with coercivity higher than 1200 kA/m.