Effect of film morphology on the magnetic properties for Nd–Fe–B thin films

The microstructure and magnetic properties of Nd–Fe–B thin films with a particulate structure were investigated. The nominal thickness of the Nd–Fe–B layer (tN) was varied from 2 to 50 nm on a (0 0 1) Mo buffer layer. The films were grown with their c-axis perpendicular to the plane, and the morphology of the film with tN=2 nm was shown to be particulate from an atomic force microscope image. The slope of the initial magnetization curve became steeper by increasing the tN value in the initial magnetization curve, indicating that the film morphology composed of single domain particles changed to that of multi-domain particles with growth. The film with tN=8 nm, which had a structure consisting of a mixture of single and multiple domain particles, showed the maximum value of the coercivity measured in the direction perpendicular to the film plane (Hc) as 19.5 kOe.