The stacking forms of thin films were as follows: MgO(001)/Mo(20 nm)/ 5/Mo(10 nm). The thin films were deposited on MgO(001) single crystal substrate with 0.5 mm thick during heating at 300☌ by using an UHV magnetron/helicon multi-target sputtering system with base pressure less than 5 × 10 −8 Pa. As mentioned above, there are various known methods of post-annealing, but the use of highly efficient lasers is an excellent technique that can significantly reduce process time and improve magnetic properties. 8,9 However, during the post-deposition annealing process in the ultra-high-vacuum, UHV, chamber, a common focused halogen lamp heater was used, which required an extremely long annealing process. Recently, we have succeeded in producing hard magnetism and controlling the perpendicular magnetic anisotropy, PMA, and in-plane magnetic anisotropy, IMA, in the Nd-Fe-B/Fe-based multilayered films by using a two-step method. The laser spot size can be adjusted to the order of mm, which is convenient for annealing small samples. The infrared lasers of CWLD with a wavelength of about 1 μm can rapidly heat up the material to be irradiated by resonant absorption and have a fast cooling rate. In contrast, continuous wave laser diode, CWLD, have the advantage of being very low cost, although they cannot be pulsed like excimer lasers. 6 However, excimer laser sources are very expensive and are used for special applications requiring non-thermal processing. The emergence of hard magnetism with large perpendicular coercivity has been reported in Nd-Fe-B thin films of 2 μm thickness irradiated with KrF excimer pulses. The infrared laser annealing process crystallizes the amorphous phase of the Nd-Fe-B layer as well as the multi-step annealing, even though the infrared laser annealing process time is only 1/100 of the process time of the multi-step annealing using halogen lamps reported previously.Īmong them, the KrF excimer laser pulses with wavelength λ of 248 nm, which are selected as a high energy source, can crystallize the amorphous phase in a very short time (ps order).
In second quadrant, squareness of demagnetization curve of infrared laser annealing processed film with Mo interlayer was better than that of film without Mo interlayer. Coercivity of in-plane annealed film with Mo interlayer was about 10 kOe which was double that of the film without Mo interlayer. Magnetic properties of both films were drasticly changed from soft magnetism to hard magnetism with in-plane magnetic anisotropy after the infrared laser annealing process at 760☌. The perpendicular magnetic anisotropy of the film with Mo interlayer was larger than that of the film without Mo interlayer before annealing. The formation of nanocomposite Nd-Fe-B/Mo/FeCo multilayered magnet films using the infrared laser annealing technique.
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