Defect induced magnetism in highly oriented pyrolytic graphite: bulk magnetization and¹⁹F hyperfine interaction studies

Abstract

We have made bulk and local investigations on defect induced magnetism in highly oriented pyrolytic graphite (HOPG) irradiated with a 40 MeV carbon beam. The local magnetic response of irradiated HOPG was studied by measuring the hyperfine field of recoil implanted (19)F using γ-ray time differential perturbed angular distribution (TDPAD) measurements. While the bulk magnetic properties of the irradiated sample show features characteristic of room temperature ferromagnetism, the hyperfine field data reflect enhanced paramagnetism with no indication of long range magnetic ordering. The experimental studies are further supported by ab initio density functional calculations. We believe that the ferromagnetic response in irradiated HOPG arises mostly from defect induced magnetic moments of carbon atoms in the near surface region, while those deep inside the host matrix remain paramagnetic.

Local magnetic behaviour of highly disordered undoped and Co-doped Bi2Se3 nanoplates: a muon spin relaxation study

“…The prejudice against magnetism in materials with filled d-or f-bands or those with only s or p electrons has been shattered in the last two decades with various observations of defectinduced magnetism in systems without magnetic ions [1][2][3][4] and the emergence of related theoretical and computational studies [5][6][7]. Topological insulators (TI's), that represent quantum materials with insulating bulk and Dirac-like gapless surface states, constitute one probable class of such materials [8,9].…”

Magnetization of Ultraviolet-Reduced Graphene Oxide Flakes in Composites Based on Polystyrene

“…It was assumed that the controlled introduction of structural defects could make graphene a promising candidate as a magnetic material suitable for spintronics. Irradiation of HOPG with various ions [ 7 , 8 ], including H + , C 4+ and N 4+ in the mega-electron-volt energy range [ 6 ] and helium [ 3 ] and iron [ 6 ] ones did not show clear indications of long-range magnetic ordering. At the same time, the magnetization data demonstrate ferromagnetic loop behavior up to room temperature.…”