[25a-E201-1~11] 10.3 Spin devices, magnetic memories and storages

▼ [25a-E201-3] Fcc(111) epitaxial magnetic tunnel junctions with a Co₉₀Fe₁₀/Mg-Al-O/Co₉₀Fe₁₀ structure

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

Keywords:TMR, (111) MTJ, spintronics

Fully epitaxial fcc(111) type MTJs with a Co₉₀Fe₁₀/Mg-Al-O (MAO) barrier/Co₉₀Fe₁₀(111) structure were fabricated on 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. Reflection high-energy electron diffraction (RHEED) and X-ray diffraction patterns confirmed (111) epitaxial growth of the Co₉₀Fe₁₀ and MAO barrier layers. Cross-sectional scanning transmission electron microscopy (STEM) images revealed flat interfaces with epitaxial growth of the stack. Due to the large mismatch between Co₉₀Fe₁₀ and MAO (~18%), periodic misfit dislocations were observed at their interfaces. Differential conductance curves were symmetric with bias polarity, indicating the similarity of bottom- and top-CoFe/MAO interfaces. The features of differential conductance were slightly different from those of a bcc(001)-Fe/MgO/Fe MTJ. This work shows the possibility of novel MTJ structures beyond the conventional bcc(001) MTJ structure.