□□ ８．2023年度研究成果概要８．１ 先端学際基幹研究部―113―We study the preparation of metal-ceramic nanogranular thin films to create novel multifunctional thin-film materials that can exhibit multiple functions from a single material and to enhance their functionality. Recently, new multi-functional properties such as "Tunnel Magneto-Dielectric (TMD) effect" and "Tunnel Magneto-Optical (TMO) effect" which can control dielectric constant and transmittance by changing magnetic field have been newly discovered in our laboratory. The effect of N2 fraction x in Ar-N2 sputtering gas on the TMD effect in Co-(Si-N) nanogranular films was investigated. Co-(Si-N) films were deposited by co-sputtering Co and Si3N4 targets in Ar- x vol.%N2 mixture gas with different N2 gas fractions x of 0-30. All deposited films had a nanogranular structure composed of Co nanogranules with a diameter of 1-3 nm embedded in a Si-N matrix. We realized the TMD effect in the films for x ≥3.3, and the film deposited in Ar-6.6 vol.%N2 gas showed the highest dielectric variations in a magnetic field. For 3.3≤ x ≤10, TMD peak frequency fTMD decreased from 17 to 40 kHz with increasing x because of the increase in intergranular spacing s. On the other hand, for 10 < x ≤30, fTMD increased from 40 kHz to 3.3 MHz as x increased since both s in the out-of-plane direction and □, which indirectly represents the measure of the distribution of s, decreased. This study provides a new way to tailor the frequency response of the TMD effect. Acknowledgments This work was supported by Tomoharu Uchiyama, Yang Cao, Hanae Kijima-Aoki, Kenji Ikeda, Nobukiyo Kobayashi, and Shigehiro Ohnuma. Published in: IEEE Transactions on Magnetics, 2023, 59(11), 28007051.□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□Si□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□150□□□□□□□□□□□□□□□□□□□□□□□SiO2□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□ □□□□□[1] T. Shimatsu, M. Uomoto, H. Fukunaga, H. Makita, Y. Suzuki, Y. Kozuka, A. Muraoka, and T. Saito, ECS Trans. 112 (3), 173-180 (2023). [2] M. Uomoto, S. Kikuchi, F. Goto, and T. Shimatsu, ECS Trans. 112 (3), 147-158 (2023). [3] H. Iemura, F. Goto, M. Uomoto, and T. Shimatsu, ECS Trans. 112 (3), 199-206 (2023). □Hiroshi MASUMOTO (Advanced Interdisciplinary Research Division/Materials and Energy Platform, FRIS) □□□□□□□□□□□□□□□□□□□□□□□□□ Effect of Ar–N2 Sputtering Gas on Structure and Tunneling Magnetodielectric Effect in Co–(Si–N) Nanogranular Films □□□□□□□□□□□□□□□□□□
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