Magnetic Properties of Quasi-One-Dimensional Crystals Formed by Graphene Nanoclusters and Embedded Atoms of the Transition Metals

Abstract

Using the density-matrix renormalization group method and quantum Monte Carlo simulation, we studied numerically the energy spectrum and thermodynamics of the quantum Heisenberg spin model for narrow graphene nanoribbons and their derivatives with periodically embedded heteroatoms. For several nanoribbon structures we found macroscopic ground state spin, gapless lowest excitation spectra and intermediate magnetization plateaus at low temperatures. We also studied the lowest energy states of frustrated systems formed by triangular graphitic clusters connected by bridged ions of transition metals. On the base of many-body perturbation theory and the exact diagonalization method, we showed the possibility of spin switching for this model due to the change the corresponding coupling parameters.

A theoretical simulation of the magnetic properties of nanocomposites based on graphene nanoflakes

“…It is of interest that for J = 0.1, the intersection point derived from ED gives the critical frustration parameter of α ~ 0.34, in good agreement with the PT estimate α ~ 0.33 from [25]. The corresponding DMRG calculations with 50 optimized states for the system formed by 210 spins yields estimates of α ~ 0.33 for s = 1/2 and α ~ 0.31 for s = 1.…”

“…We cannot perform a similar analysis for the model systems of Figure 1A,B since the corresponding first‐order PT corrections to the ground state energy equals to zero. It is also of interest to study the case of intermediate values of coupling J for which the PT consideration of references [25, 30] cannot be applied.…”

“…These interactions may be of the same order as the interaction with the corresponding nearest neighboring spin. In the result we obtain a frustrated spin system similar to the chain model shown in Figure 3 which has been studied in reference [25] by means of first‐order perturbation theory with respect to the interactions between structural units.…”

“…The interaction between CTM and nearest graphene nanoflake may also involve next nearest neighbor spins of the nanoflake. This leads to the frustrated character of the corresponding spin lattice and may affect the system's ground-state spin [25]. To study this, we apply the ED method to obtain the energy spectra of the spin Hamiltonians of small lattice clusters.…”

Quantum‐phase transitions in 1D Heisenberg spin systems

“…The theoretical characterization of novel, highly correlated systems is an ongoing challenge, with much recent effort focused on low-dimensional circumstances. Here, we study the peculiarities of the energy spectrum and the magnetic properties of quasione-dimensional (quasi-1D) Heisenberg spin systems with antiferromagnetically signed couplings between neighboring spins motivated by a large number of successful and potential applications, say to address magnetic properties of polymeric complexes of the transition metal compounds, [1,2] stacked crystals of ion-radical salts, [3][4][5] organic polymers with conjugated bonds, [6][7][8] and so on.…”