[20a-B101-1~10] 10.3 スピンデバイス・磁気メモリ・ストレージ技術

▲ [20a-B101-10] [Young Scientist Presentation Award Speech] Fcc(111) epitaxial magnetic tunnel junctions with
a Co₉₀Fe₁₀/Mg-Al-O/Co₉₀Fe₁₀ structure

〇Jieyuan Song^1,2、Thomas Scheike²、Cong He²、Zhenchao Wen²、Hiroaki Sukegawa²、Tadakatsu Ohkubo²、Kazuhiro Hono²、Seiji Mitani^1,2 (1.Tsukuba Univ.、2.NIMS)

キーワード：TMR, (111) MTJ, spintronics

Fully epitaxial fcc(111) type MTJs with a Co₉₀Fe₁₀/Mg-Al-O (MAO) barrier/Co₉₀Fe₁₀(111) structure were fabricated on a sapphire (0001) single crystal substrate with a high-quality Ru buffer layer. The prepared MTJs show a TMR ratio of 37% at room temperature and 47% at 10K, which are the first TMR observation of this novel structure. Co₉₀Fe₁₀ was used to obtain fcc single-phase layers which were confirmed by the XRD in-plane φ-scan spectrum. A fully epitaxial (111) MTJ stack from Ru buffer to top Co₉₀Fe₁₀ was confirmed by reflection high-energy electron diffraction (RHEED) and the cross-sectional scanning transmission electron microscopy (STEM). Although there is a large mismatch between Co₉₀Fe₁₀ and MAO (~18%), STEM images indicate the relatively flat barrier interfaces due to introducing periotic misfit dislocations. Differential conductance curves were symmetric with bias polarity, indicating the similar quality of bottom- and top-CoFe/MAO interfaces. This work shows the possibility of improving the novel MTJ structures as a new large TMR candidate beyond the conventional bcc(001) MTJs.