[22p-P02-1~10] 10 Spintronics and Magnetics(Poster)

▲ [22p-P02-2] Anisotropic orbital moment induced at graphene / L1₀-alloy hybrid interface

〇Hiroshi Naganuma¹, Masahiko Nishijima¹, Hayato Adachi², Mitsuharu Uemoto², Hikari Shinya¹, Sintaro Yasui³, Hitoshi Morioka⁴, Bruno Dlubak⁵, Pierre Seneor^5,6, Kenta Amemiya⁷ (1.Tohoku Univ., 2.Kobe Univ., 3.Tokyo In. Tech., 4.BurkerJapan, 5.CNRS/Thales, 6.ParisSud., 7.KEK)

Keywords:Graphene, L10-ordered alloy, interfacial perpendicular magnetic anistropy

Hexagonal-graphene (Gr) by chemical vapor deposition was formed on tetragonal(L1₀)-FePd epitaxial film by r.f. magnetron sputtering, which is crystallinely heterogeneous interface. The interatomic distance between Gr layer and the outermost surface Fe layer was approximately 0.2 nm, which was shorter than the interatomic distance between the upper Gr layer (0.38 nm). FePd film had a high degree of L1₀-ordering up to the outermost surface of the atoms, and the outermost surface atoms were identified as Fe. The unit cell of L1₀-FePd at the interface was slightly expanded to c-axis when compared to the inner layer of FePd, and the interface L1₀-FePd layer shows a high mass-density. The depth-resolved X-ray absorption and X-ray magnetic circular dichroism analysis revealed an anisotropic orbital magnetic moment to the perpendicular direction was induced at the FePd-side of Gr/FePd interface. The anisotropic orbital magnetic moment robustly changed rather than gradually change at a 1-nm-thick depth, which was same tendency of that observed in the structural analyses. This means that the robust interfacial induced perpendicular magnetic anisotropy (IPMA) is added to the large perpendicular magnetocrystalline anisotropy (PMA) of L1₀-ordered alloy. By assuming both of PMA and IPMA in micromagnetic simulation based on string-method, it was predicted that Gr / L1₀-FePd hybrid magnetic tunnel junctions realized a 10-year data-retention in a very small recording layer with circular diameter and thickness of 10 nm and 2 nm, which is attracted for high density magnetic random access memory application.