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Spin Gap in Two-Dimensional Heisenberg Model for CaVO
We investigate the mechanism of spin gap formation in a two-dimensional model
relevant to Mott insulators such as CaVO. From the perturbation
expansion and quantum Monte Carlo calculations, the origin of the spin gap is
ascribed to the four-site plaquette singlet in contrast to the dimer gap
established in the generalized dimerized Heisenberg model.Comment: 8 pages, 6 figures available upon request (Revtex
Magnetic Susceptibility for
We examine experimental magnetic susceptibility for
CaVO by fitting with fitting function .
The function is a power series of 1/T and the lowest order
term is fixed as , where is the Curie constant as determined by the
experimental -value (g=1.96). Fitting parameters are , and
expansion coefficients except for the first one in .
We determine and as 0.73 and 0 for an
experimental sample. We interpret as the volume fraction of
CaVO in the sample and as the susceptibility for the
pure CaVO. The result of means that the sample includes
nonmagnetic components. This interpretation consists with the result of a
perturbation theory and a neutron scattering experiment.Comment: 4pages, 4figure
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