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Magnetic properties of the spin doughnut Mo_{75}V_{20}, which is a frustrated magnetic cluster with twenty spins, are studied by using the finite-temperature Lanczos method. Our model Hamiltonian consists of one ten-spin ring and two five-spin rings with nearest-neighbor antiferromagnetic couplings J and J. The five-spin rings are coupled to the ten-spin ring by an antiferromagnetic exchange interaction J so as to form isosceles triangles of one J-bond and two J-bonds. Fitting the theoretical magnetic susceptibility with the experimental one measured by Muller et al., the exchange parameters are estimated as J=388 K, J=163 K and J=81 K. The most interesting feature of this system is that the two five-spin rings behave like two free-spins at low temperatures in despite of J>J. We also calculate temperature dependence of the specific heat, and find three peaks at T sim J, J and J/100.
The spin-1/2 triangular lattice antiferromagnet YbMgGaO$_{4}$ has attracted recent attention as a quantum spin-liquid candidate with the possible presence of off-diagonal anisotropic exchange interactions induced by spin-orbit coupling. Whether a qua
Magnetism of transition metal (TM) oxides is usually described in terms of the Heisenberg model, with orientation-independent interactions between the spins. However, the applicability of such a model is not fully justified for TM oxides because spin
We derive a set of equations expressing the parameters of the magnetic interactions characterizing a strongly correlated electronic system in terms of single-electron Greens functions and self-energies. This allows to establish a mapping between the
We perform inelastic neutron scattering measurements on the molecular nanomagnet Mn_12-acetate to measure the excitation spectrum up to 45meV (500K). We isolate magnetic excitations in two groups at 5-6.5meV (60-75K) and 8-10.5meV (95-120K), with hig
The applicability of a broken symmetry version of the $G_0W_0$ approximation to the calculation of isotropic exchange coupling constants has been studied. Using a simple H--He--H model system the results show a significant and consistent improvement