We will demonstrate that ultrasonic treatment of a graphite crystal in water can lead to the formation of small graphene-like flakes in solution. The delamination of the graphite can be increased dramatically by intercalation of bromine from a Br2-saturated water solution. After ultrasonic treatment, large amounts of graphene-like flakes with varying thickness are observed in SEM and TEM. They can be adsorbed onto a surface of a suitable substrate by a simple dipping technique. The effect of polar and non-polar solvents as well as adsorption of the graphene on hydrophobic and hydrophilic substrates will be demonstrated and compared. DFT calculations of the intercalation process have been carried out using the SIESTA package and the effect of bromine intercalation on cohesive energy and electronic structure will be discussed and compared with experimental data. Finally, the general approach of using ultrasonic treatment and intercalation as a facile route to graphene synthesis compared to other methods will be discussed.

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Quantum fluctuations in many-spin magnetic molecules

Physical review. B, Condensed matter (1998)

А. К. Звездин V. V. Dobrovitski B. N. Harmon M. I. Katsnelson

A new type of mesoscopic quantum effect in large-spin molecules possessing easy-axis anisotropy, such as Mn12, is predicted. The response of such a system to an external field applied perpendicular to the easy axis is considered. It is shown that the susceptibility of this system exhibits a peculiar peak of purely quantum origin. This effect arises from very general properties of quantum fluctuations in spin systems. We demonstrate that the effect is entirely accessible for contemporary experimental techniques. Our studies show that the many-spin nature of the Mn12 clusters is important for a correct description of this quantum peak.

Mesoscopic physics

Quantum fluctuation

10.1103/physrevb.58.r14733

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Role of direct exchange and Dzyaloshinskii-Moriya interactions in magnetic properties of graphene derivatives: C2F and C2H

Physical review. B./Physical review. B (2016)

В. В. Мазуренко А. Н. Руденко S. A. Nikolaev Darya Medvedeva A. I. Lichtenstein

According to Lieb's theorem the ferromagnetic interaction in graphene-based materials with bipartite lattice is a result of disbalance between the number of sites available for ${p}_{z}$ electrons in different sublattices. Here we report on another mechanism of the ferromagnetism in functionalized graphene that is the direct exchange interaction between spin orbitals. By the example of the single-side semihydrogenated (${\mathrm{C}}_{2}\mathrm{H}$) and semifluorinated (${\mathrm{C}}_{2}\mathrm{F}$) graphene we show that such a coupling can partially or even fully compensate antiferromagnetic character of indirect exchange interactions reported earlier [Phys. Rev. B 88, 081405(R) (2013)]. As a result, ${\mathrm{C}}_{2}\mathrm{H}$ is found to be a two-dimensional material with the isotropic ferromagnetic interaction and negligibly small magnetic anisotropy, which prevents the formation of the long-range magnetic order at finite temperature in accordance with the Mermin-Wagner theorem. This gives a rare example of a system where direct exchange interactions play a crucial role in determining a magnetic structure. In turn, ${\mathrm{C}}_{2}\mathrm{F}$ is found to be at the threshold of the antiferromagnetic-ferromagnetic instability, which in combination with the Dzyaloshinskii-Moriya interaction can lead to a skyrmion state.

Exchange interaction

Lattice (music)

10.1103/physrevb.94.214411

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Self-consistent spin-wave theory of two-dimensional magnets with impurities

Physical review. B, Condensed matter (1999)

V. Yu. Irkhin A. A. Katanin M. I. Katsnelson

The self-consistent spin-wave theory is applied to investigate the magnetization distribution around the impurity in isotropic and easy-axis two-dimensional ferro- and antiferromagnets. The temperature dependences of the host magnetization disturbance and impurity magnetization are calculated. The short-range order in the isotropic case is investigated. The importance of dynamical and kinematical interactions of spin waves is demonstrated.

Spin wave

Orbital magnetization

10.1103/physrevb.60.14779

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Erratum: Toward a realistic description of multilayer black phosphorus: FromGWapproximation to large-scale tight-binding simulations [Phys. Rev. B92, 085419 (2015)]

Physical review. B./Physical review. B (2016)

А. Н. Руденко Shengjun Yuan M. I. Katsnelson

In the original version of the paper, the magnitudes of the hopping parameters t 5 and t ⊥ 5 appearing in Table II were misprinted.The correct values are +0.019eV and +0.005 eV, respectively.Additionally, the hopping parameter t ⊥ 5 was missing in the original version of Fig. 3. Revised versions of Table II andFig.3 are provided with this Erratum.The results presented in the original paper were obtained with the correct hopping parameters.Insignificant changes of the results are expected with the parameters given in the original paper.Finally, the expression for the Fermi-Dirac occupation factor given in Sec.III C should read f nk = (exp(βε nk ) + 1) -1 .

10.1103/physrevb.93.199906

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Citations (16)