[21a-P02-1~50] 10 Spintronics and Magnetics(Poster)

[21a-P02-8] Interpretation of directionality XAS and XMCD spectrum in twisted L1₀-FePd/Graphene interface by first-principles calculation

〇Hiroshi Naganuma^1,2,3, Mitsuharu Uemoto⁴, Hayato Adachi⁴, Hikari Shinya⁵, Izumi Mochiduki⁶, Akihiko Hirata⁷, Bruno Dubluk⁸, Tomoya Ono⁴, Pierre Seneor^8,9,2, Kenta Amemiya⁶ (1.CIES, Tohoku Univ., 2.CSIS, Tohoku Univ., 3.Grad., Tohoku Univ., 4.Kove Univ., 5.RIEC,Tohoku Univ., 6.IMSS, KEK, 7.Waseda Univ., 8.CNRS/Thales, 9.Univ.Paris-Sac.)

Keywords:Graphene, L10-ordered alloy, moire

The heterogeneous crystal interface of hexagonal graphene and tetragonal L1₀-FePd ordered alloy are bonded by van der Waals forces. In our previous study, we presented [22p-P02-2, in JSAP, 2021] that a robust interfacial perpendicular magnetic anisotropy was excited at the L1₀-FePd/graphene interface (H. Naganuma et al, ACS Nano, 2022). This study focused on the chemical bonding and magnetic properties of the graphene at the L1₀-FePd/ graphene interface. X-ray absorption (XAS) by different angles showed that the π* orbital peak was observed not only at a nominal incident angle (q_NI = 90°) but also at a glance incident angle (q_GI = 30°). From the first-principles calculation, the π* orbital peak observed at a tilted angle (q_GI = 30°) is attributed to the strong chemical bonding of Fe in FePd and C in graphene owing to the close location of the p_z orbital of C and d_z orbital of Fe orbital at the fermi level. The p_z orbital of the π* bonding in C twists into the xy plane direction owing to the chemical bonding with the Fe or the perturbation of the Fe ion to the carbon orbital which is the reason for the twisted interface bonding and the wavy graphene. From the simulation of scanning transmission electron microscopy (STEM), moiré-like contrast was observed between Fe in L1₀-FePd and graphene owing to the twisted interface and periodic displacement of C in graphene. In other words, the twisted and periodic displacement can be experimentally observed with STEM images but not with angular XAS. The X-ray magnetic dichroism (XMCD) spectrum of C in graphene did not show an obvious magnetic moment. It can be interpreted by the first-principles calculation that the XMCD signal was not observed because only the spin moment, not the orbital moment, was induced in the C in graphene.