Relationship between target materials and various properties of PLD-made isotropic Nd-Fe-B films

Abstract

In order to deposit isotropic Nd-Fe-B film magnets on metal substrates, a laser beam with an energy density of approximately 3 J/cm2 was defocused on the surface of Nd-Fe-B sintered targets with three densities of 5.69, 6.14, and 6.64 g/cm3, respectively. The different Nd content (Nd/(Nd + Fe)) between each film and the corresponding targets decreased as the density of the targets increased. We have reported that the deposition using a Nd-Fe-B alloy target under the same laser energy density and T-S distance enabled us to obtain the good transfer of composition from an alloy target to a film. It was clarified that the similar result could be obtained in the use of a sintered target with the density of 6.64 g/cm3. Comparison of magnetic properties, normalized demagnetization curves, and microstructure between the films prepared using a sintered target (6.64 g/cm3) and a Nd-Fe-B alloy target, respectively, was carried out. The values of coercivity and (BH)max of the samples prepared by the sintered target were higher than those of the films prepared using the alloy one. Moreover, the use of a Nd-Fe-B sintered target enabled us to improve the reproducibility of squareness in demagnetization curves. It is considered that the results of comparison are attributed to the different microstructure of the films such as the precipitation due to uneven distribution of α-Fe and Nd elements. We also suppose that the formation of microstructure in each film originates from the microstructure of the corresponding targets.