Abstract
We consider triangular graphone structure – a semi-hydrogenated layer of graphene with hydrogen atoms boned to one of its sub-lattices only. The response function of graphone to an external magnetic field is evaluated in general using the Heisenberg Hamiltonian model of the structure with exchange energy coefficient J 0 of unknown value (negative due to ferromagnetic behaviour of triangular graphone). The spin wave approach in the limit of near zero temperature is used for the description of the magnetisation. A specific case when the graphone is exposed to a magnetic pulse with a given carrier frequency is examined in greater depth. To obtain the magnetization response, integration over both the frequency space and momentum space is necessary. Due to inapplicability of the isotropic approximation for the given geometry of graphone, integration over momentum space is performed numerically. The calculations show that the resonance of the system occurs at frequencies which correspond to the upper limit of the spin wave energy band and the saddle points of the energy surface. Using these results, further experimental investigation based on THz or far-infrared spectroscopy can be performed, which can determine the as-yet-unknown exchange energy coefficient J 0 . The coefficient can in turn provide an estimate of a temperature range for which the spin wave approach utilised in our investigation is valid.
Highlights
Over the last decades, graphene has gained increasing attention due to its two-dimensional planar structure, band crossing at the Dirac points, two sub-lattice semi metallic conduction and its possible use in nanoelectronics [1,2,3,4,5]
We focus on triangular graphone structure
According to the works of Zhou et al, computer simulations based on spin-polarized density functional theory suggest that these interactions result in ferromagnetic properties of graphone [12]
Summary
Graphene has gained increasing attention due to its two-dimensional planar structure, band crossing at the Dirac points, two sub-lattice semi metallic conduction and its possible use in nanoelectronics [1,2,3,4,5]. Graphene does not exhibit strong magnetic properties, but only weak antiferromagnetic order [6, 7] Several methods such as functionalization of graphene by chemisorptions of atomic hydrogen have been proposed to tune electronic properties and induce magnetic behaviour [8,9,10,11]. According to the works of Zhou et al, computer simulations based on spin-polarized density functional theory suggest that these interactions result in ferromagnetic properties of graphone [12] It possesses an energy gap, making it an attractive material for use in nano-electronics [7, 12,13,14,15]. Substrate creates dipole moments for each nitrogen site that break the equivalency of two carbon atoms in two different graphene sub-lattices, suppressing the hydrogen migration
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