Studies on Magnetism of Transition Metal Layers Deposited on Graphene
Chih-Heng Huang1,2*, Tzu-Hung Chuang2, Chung-I Lu2, Yao-Jui Chan3, Kun-Ta Lu2, Chien-Chen Kuo1,3
1Program for Synchrotron Radiation and Neutron Beam Applications, National Sun Yat-sen University, Kaohsiung, Taiwan
2National Synchrotron Radiation Research Center, Hsinchu, Taiwan
3Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan
* presenting author:Chih-Heng Huang,
Magnetism of organic molecules and carbon atoms has attracted much attention. Among these materials, graphene, a single layer of carbon atoms, has been investigated intensively. Theoretical studies on transition metal induced magnetism of graphene has been reported [1-2], while growing such homogeneous thin film experimentally remains challenging. On the other hand, intercalation of cobalt through graphene has shown relatively strong ferromagnetism in cobalt, and anti-ferromagnetism in carbon, which is a candidate of layered magnetic materials [3].
Here we report our recent studies on magnetism of transition metal layers deposited on graphene by photoemission electron microscope (PEEM) and magneto-optical Kerr effect (MOKE). Single layer graphene was prepared on Pt(111) single crystal, which is believed to be a quasi free-standing graphene [4]. The quality and lattice orientation of graphene were checked by low energy electron diffraction (LEED) and x-ray absorption spectroscopy. Metallic layers were deposited at room temperature via thermal deposition. The macroscopic magnetism probed by MOKE measurements shows that the Fe thin film of the thickness thicker than 11 monolayers has ferromagnetic order. For 20 monolayers of Fe deposited on graphene, strong magnetic anisotropy is observed. Spatially resolved magnetic domains are investigated by PEEM at BL05B2 end-station of Taiwan Light Source. For 20 monolayers of Fe and above, magnetic domains have a needle-like shape with the orientation corresponding to the macroscopic magnetic anisotropy.

[1] Chao Cao et. al., Phys. Rev. B (81), 205424 (2010)
[2] Yudistira Virgus et. al., Phys. Rev. Lett. 113, 175502 (2014)
[3] H. Vita et. al., Phys. Rev. B 90, 165432 (2014)
[4] Peter Sutter et. al., Phys. Rev. B 80, 245411 (2009)

Keywords: Graphene, Magnetism, PEEM