わずか50℃が、平坦か崩壊かを分ける ― L10-FePd膜を蝕む”膜の崩壊”を、二段階焼成の最初の一手で封じ込める ―

2026-08-04 富山大学

図1 二段階焼成法によるL1₀-FePd極薄膜の「平坦性」と「規則化」の両立と、Dewettingの抑制

＜関連情報＞

• https://www.u-toyama.ac.jp/news-press/138595/
• https://www.sciencedirect.com/science/article/pii/S092583882603820X

2段階加熱と固体脱湿を利用した高秩序L10 – FePd合金エピタキシャル膜 Harnessing two-step heating and solid-state dewetting for highly ordered L10-FePd alloy epitaxial films

Samuel Vergara, Shingo Maruyama, Soki Yoshida, Hanuma Kumar Dara, Keisuke Haruki, Naohiro Matsumoto, Mitsuharu Uemoto, Tomoya Ono, Shintaro Yasui, Yasushi Endo, Amit Kohn, Masaki Mizuguchi, Tomoyuki Ogawa, Hiroshi Naganuma
Journal of Alloys and Compounds  Available online: 26 July 2026
DOI:https://doi.org/10.1016/j.jallcom.2026.189751

Highlights

• Two-step heating enables morphology control unreachable by one-step heating.
• 50 K Ts shift switches FM, SSD, and SK/late-stage SSD growth regimes.
• FM at 150°C yields flat L10-FePd with strong PMA and high Mr/Ms.
• SSD at 200–250°C achieves SL10 = 0.99 and PMA = 1.33 MJ/m3.
• Results enable ultra-thin L10-FePd films for next-generation MRAM.

Abstract

L1₀-ordered FePd epitaxial films with a nominal thickness of 5 nm were grown by r.f. magnetron sputtering on the SrTiO₃ (001) single crystal substrates by a two-step heating method. A subtle 50 K change in the first-heating temperature of a two-step process drastically alters the morphological trajectory of L1₀-FePd films, switching among three regimes: (i) Frank–van der Merwe (FM — atomically flat), (ii) Solid-state dewetting (SSD — square holes), and (iii) Stranski-Krastanov or late-stage SSD (SK or SSD late stage — 3D grains). (i) [FM mode] Almost no lattice disturbance in the in-plane direction, and perfect constraint by tensile strain from the SrTiO₃ substrate was achieved. (ii) [SSD mode] Square holes penetrating to the SrTiO₃ substrate were formed, and sides of the square were grown along the < 100 > or < 010 > of the SrTiO₃ substrate. According to first-principles calculations, a large difference in surface free energy between L1₀-FePd and the SrTiO₃ substrate is predicted. This difference in surface free energy is the minimum necessary condition for SSD to occur. The trigger for SSD is small holes/voids formed during the 1st heating process in the two-step heating process. (iii) [SK or late-stage SSD mode] Grains grew 3-dimensionally, which can be considered as SK growth mode or the late stages of SSD. Note that the 1st heating temperature of the two-step heating process significantly changed the morphological trajectory, even though the 2nd heating temperature of 600°C was significantly higher than that of the 1st growth temperature. The SSD reduced the substrate restraint, resulting in the highest degree of L1₀-ordering (S_L10 = 0.99) and the highest perpendicular magnetic anisotropy (PMA = 1.33MJ/m³).