Atomic-scale magnetism of cobalt-intercalated graphene

Abstract

Using spin-polarized scanning tunneling microscopy and density functional theory, we have studied the structural and magnetic properties of cobalt-intercalated graphene on Ir(111). The cobalt forms monolayer islands being pseudomorphic with the Ir(111) beneath the graphene. The strong bonding between graphene and cobalt leads to a high corrugation within the Moiré pattern which arises due to the lattice mismatch between the graphene and the Co on Ir(111). The intercalation regions exhibit an out-of-plane easy axis with an extremely high switching field, which surpasses the significant values reported for uncovered cobalt islands on Ir(111). Within the Moiré unit cell of the intercalation regions, we observe a site-dependent variation of the local effective spin polarization. State-of-the-art first-principles calculations show that the origin of this variation is a site-dependent magnetization of the graphene: At top sites the graphene is coupled ferromagnetically to the cobalt underneath, while it is antiferromagnetically coupled at fcc and hcp sites.

Cobalt intercalation at the graphene/iridium(111) interface: Influence of rotational domains, wrinkles, and atomic steps

“…For example, the intercalation of noble metals [2,3] or hydrogen atoms [4] can be used to reduce the interaction between graphene and its substrate, and even restore the electronic properties of free-standing graphene, while the intercalation of alkali metals is an efficient mean to control the doping level of graphene [5]. Intercalation of a ferromagnetic transition metal can also enhance the net magnetic moment induced in carbon atoms when graphene is in contact with a magnetic surface [6], and is a promising route to fabricate graphene/ferromagnetic metal hybrid structures with perpendicular magnetic anisotropy [7,8].Understanding where and how a foreign species intercalates below graphene is a challenging task, and different scenarios have been proposed. While oxygen intercalates at the free edges of graphene grown on Ru(0001) [9, 10] and on Ir(111) [11], alkali metals instead may intercalate at the substrate step edges or at boundaries between different rotational domains in graphene/Ni(111) [5] and in graphite [12].…”

“…For example, the intercalation of noble metals [2,3] or hydrogen atoms [4] can be used to reduce the interaction between graphene and its substrate, and even restore the electronic properties of free-standing graphene, while the intercalation of alkali metals is an efficient mean to control the doping level of graphene [5]. Intercalation of a ferromagnetic transition metal can also enhance the net magnetic moment induced in carbon atoms when graphene is in contact with a magnetic surface [6], and is a promising route to fabricate graphene/ferromagnetic metal hybrid structures with perpendicular magnetic anisotropy [7,8].…”

Probing Electronic Properties of Graphene on the Atomic Scale by Scanning Tunneling Microscopy and Spectroscopy

“…Decker et al investigated the structural and magnetic properties of cobalt-intercalated graphene on Ir(111) by using spin-polarized STM [114]. They observed a site-dependent variation of the local e ective spin polarization, as shown in Figure 11, which was attributed to a site-dependent magnetization of the graphene [114].…”

First-principles modeling of magnetic misfit interfaces

“…1. In fact, such patterns have been observed experimentally in a wide range of interfaces, such as graphene/Ir, 10,11 Au/Co, 12,13 Pt/Co, 14 FeO/Pd, 15 FeO/Pt, 16 and Fe/MgO. 17 By means of Moiré supercells, the strain on the component materials can be reduced significantly.…”