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Size dependence of the magnetic response of graphite oxide and graphene flakes – an electron spin resonance study
Author(s) -
Ćirić Luka,
Sienkiewicz Andrzej,
Djokić Dejan M.,
Smajda Rita,
Magrez Arnaud,
Kaspar Tommy,
Nesper Reinhard,
Forró László
Publication year - 2010
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201000448
Subject(s) - graphene , electron paramagnetic resonance , spins , materials science , superparamagnetism , oxide , condensed matter physics , curie temperature , graphite oxide , spin (aerodynamics) , ferromagnetic resonance , nanotechnology , nuclear magnetic resonance , ferromagnetism , magnetization , physics , magnetic field , metallurgy , thermodynamics , quantum mechanics
We employed electron spin resonance (ESR) technique in the investigation of a series of graphene flakes with different size distributions. Graphene oxide (GO) samples with three distinct size distributions were prepared by the Brodie method. Large flakes of ∼2500 µm 2 , intermediate size flakes of ∼1 µm 2 , and small ones of ∼500 nm 2 have been characterized by ESR in the 4–295 K temperature range. Already for GO flakes the magnetic response strongly varies with their size. Large GO flakes are inhomogeneous, revealed by the presence of both Pauli and Curie components in the overall signal. In small GO flakes ESR spin susceptibility reveals superparamagnetic behavior ascribed to interaction between localized spins. The intermediate flakes show a standard Curie behavior showing a uniform oxidation and the concomitant non‐interacting localized spins. On this batch a thermal method of reduction was applied such that in polar solvent the suspension of GO was heat treated at temperatures below 200 °C. ESR susceptibility shows that this reduction can recover some of the Pauli‐like contribution of the pristine graphene. However, our study shows that the full optimization of oxidation/reduction parameters is yet to be achieved.