Defect induced magnetic interactions in highly oriented pyrolytic graphite (HOPG): a local investigation using TDPAD method

Abstract

We performed microscopic studies of the magnetic interaction in HOPG by measuring the hyperfine field of 19 F using the time differential perturbed angular distribution (TDPAD) technique. The results show two hyperfine fields (B hf ) components: one varying strongly with temperature and saturating around 5 kG, while the other showing a maximum of 0.85 kG. The temperature dependence of B hf does not show any signature of ferromagnetic ordering, but is reminiscent of enhanced paramagnetism.

Determination of the hyperfine magnetic field in magnetic carbon-based materials: DFT calculations and NMR experiments

“…Therefore, evidence for B hf and measurements of its properties are highly desirable for a better understanding of magnetism in carbon-based materials, providing information on the source of magnetism from a local perspective. Besides its importance from a fundamental point of view, the hyperfine interactions are relevant for applications of graphene and related materials in spintronics and quantum information processing 27 28 29 30 , leading to numerous theoretical calculations 27 28 31 and experimental investigations involving the use of different techniques – electron spin resonance (ESR) 11 , muon spin rotation ( μ SR) 32 and perturbed angular distribution (PAD) 33 . In none of these reports, however, any clue about the B hf value in a truly ferromagnetic carbon material was ever reported.…”

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

“…Calculation of CSR sizes according to X-ray diffraction analysis data for GO and UV-rGO using the Scherrer method (1) . Note: (1) Scherrer's constant is 0.9; irradiation was performed with the Kα 1 -line of copper with a wavelength λ = 0.15418 nm; (2) symbol for a carbon filler of a polymer matrix in a composite; (3) doubled Bragg diffraction angle; (4) full width at half height of the reflex at 2θ; (5) ; D p -average CSR size according to the Scherrer formula; (6) d-the distance between adjacent crystallographic planes; (7) n-number of graphene layers in a multilayer graphene stack.…”

“…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.…”

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

“…Despite the large number of experimental and theoretical results available, there has been skepticism regarding the long range bulk ferromagnetism in graphite because the magnetic signals are generally weak (≤3 × 10 −3 emu g −1 ) and the Curie temperature exceeds 300 K [4]. Furthermore, hyperfine field measurements for 19 F in HOPG under conditions of zero applied magnetic field [18,17] using the perturbed angular correlation (PAC) method did not show the presence of a detectable static magnetic hyperfine field. In view of the above facts, further investigations are desirable, especially using local techniques sensitive to magnetic interactions.…”