Presentation Information
[P1-66]Preparation of micromagnets via LIFT technique
*Masaki Nakano1, Gakuto Tahara1, Takuki Amiya1, Akihiro Yamashita1, Takeshi Yanai1, Masaru Itakura2, Kunihiro Koike3, Hirotoshi Fukunaga1 (1. Nagasaki university (Japan), 2. Kyushu university (Japan), 3. Yamagata university (Japan))
Keywords:
micromagnets,LIFT technique,PLD method
Although our group has focused on the fabrication of rare-earth film magnets using a Pulsed Laser Deposition method [1], these samples require high-temperature heat treatment above 723 K, such as substrate heating or post-annealing, to obtain hard magnetic properties. At present, film magnets are expected to be used in MEMS, and a fabrication method employing lower temperatures is required to facilitate compatibility with other devices and low-melting-point materials in MEMS. Recently, we prepared Nd-Fe-B film magnets fabricated by the aforementioned PLD as donors and successfully prepared Nd-Fe-B micromagnets using a Laser Induced Forward Transfer technique [2]. In the technique, a specimen is prepared on a laser-transparent glass substrate, subsequently subjected to heat treatment, and irradiated by a laser from the donor side, resulting in the deposition of a transfer film on the receiver substrate. However, the coercivity of current micromagnets is only approximately 200 kA/m [2] compared to the coercivity of the donor exceeding 200 kA/m. In this study, we report the effects of energy density in the LIFT technique on the coercivity of Nd-Fe-B micromagnets of various thicknesses. Nd-Fe-B micromagnets were deposited in a high vacuum using a YAG laser with a wavelength of 355 nm and a repetition rate of 30 Hz. NdFe-B film magnets fabricated by PLD were used as donors, and Ta substrates were used as receivers. In this experiment, the energy density of the laser beam was controlled by the spot size and power of the laser. Figure 1 illustrates the comparison of the coercivity values between donors and receivers by modulating the laser energy density in relation to the donor film thickness. A correlation between the coercivity of the donor and receiver was observed for the ratio of film-thickness to energy-density between 4 and 9 microns/(J/cm2). Micromagnets with coercivity of approximately 500 kA/m could be obtained through modulation of the energy density, representing a significant enhancement over the previously reported maximum value [2]. X-ray diffraction patterns of the two samples prepared with varying thickness-to-energy density ratios were observed. Under optimal conditions, a prominent Nd2Fe14B phase was observed, whereas the α-Fe peak was suppressed. These findings suggest that the previously reported inability to achieve improved coercivity may be attributed to the application of suboptimal laser energy density for a given film thickness. References [1]Nakano et al., IEEE Trans. Magn., 56, (2020) #7516303. [2]Nakano et al., IEEE Trans. Magn., 60, (2024) #2100604.
