Magnetic properties of Nd-Fe-B thick film magnets prepared by laser ablation technique

Summary form only given In order to advance micro-machines such as small motors in mobile phones, Nd-Fe-B films with the thickness of several tens of microns are strongly needed. Although a sputtering method is convenient to obtain film magnets, we have difficulty in realizing a high deposition rate. In this contribution, we succeeded the high deposition rate of 50 /spl mu/m/h using the laser ablation technique. Suppression of oxidation of a key point to obtain Nd-Fe-B film magnets with high coercivity, therefore we used the following methods. (1) Ta substrates and a Ti sublimation pump used as an auxiliary pump were used during deposition. (2) The composition of a target was set to Nd2.6Fe14B which included a larger amount of Nd compared with the stoichiometric composition of Nd2Fe14B. hi addition, the distance between a target and a substrate was set at approximately 5mm to realize a high deposition rate. One-hour-deposition using laser ablation technique enabled us to obtain Nd-Fe-B amorphous films with the thickness of approximately 50 microns. The authors show the coercivity of Nd-Fe-B films as a function of annealing time t/sub a/ at the temperatures of 823, 923 and 1023 K. The annealing time ta indicates the time after the temperature reached a preset temperature. We obtain the H/sub c/ value lager than 800 kA/m for t/sub a/ = 0 at 923 K. This value was the highest one through our experiments. They also show the hysteresis loop of a sample fabricated under the same condition. It was clarified that approximately 50 micron-thick Nd-Fe-B film magnets with the H/sub c/ value of more than 800A/m, I/sub r/ of approximately 0.6 T and (BH)/sub max/ of 56 kJ/m/sup 3/ can be obtained.