Magnetic properties of Nd-Fe-B/α-Fe multi-layered thick film magnets

Nd-Fe-B/α-Fe multi-layered nanocomposite film-magnets were prepared from a rotating Nd2.6Fe14B/α-Fe composite target by the pulse laser deposition method with a NdYAG laser (λ=355 nm). The prepared film-magnets were composed of approximately 800 layers with the thickness of about several tens nanometre, and exhibited hard magnetic properties after annealing. The laser power for the ablation of the target was varied between 3 and 7 W, and it was found that the composition, magnetic properties, and the surface roughness of the prepared films depend on the laser power. A reduction in the laser power caused increases in remanence and the maximum energy product (BH)max as well as decreases in Nd content and coercivity of the films. All the samples had Nd-poor compositions compared with that of the Nd2.6Fe14B target and the Nd-contents of the films deposited with laser power of 3 W were less than that of the stoichiometric composition of Nd2Fe14B. The highest (BH)max and remanence values were obtained for a film deposited with laser power of 3 W, and were 90 kJ/m and 1.0 T, respectively. The obtained high remanence value is discussed from the viewpoint of the remanence enhancement as well as the large saturation magnetization of α-Fe .