Spin Gap in β-TeVO4: a Quantum Monte Carlo Study

In this paper, we proposed a two-leg spin ladder model for the description of magnetic properties of the beta-TeVO4 compound. Quantum Monte Carlo (QMC) simulation was applied to describe the temperature-dependent magnetic susceptibility data for low temperatures. The two-leg spin ladder model presents a spin gap, and we suggests that beta-TeVO4 compound presents such a spin gap also, and therefore, the model proposed here can be experimentally tested by measuring the spin gap of the compound. The susceptibility phase diagram has a rounded peak in the vicinity of T approximate to 12.2 K and obeys Troyer's law for low temperatures and Curie's law for high temperatures. We also study the susceptibility diagram in low temperatures and found the spin gap Delta = 8.06 K. The linearization of the equation for susceptibility in low temperatures allows us to obtain the spin gap value, and such a linearization was made with the data from the QMC simulation. In all the results, there is a very good agreement with the experimental data. We also show that the spin gap is null and the susceptibility is proportional to T for low temperatures when relatively high values of the ladders' coupling is considered. The theoretical results are compared with other studies as well as applied to describe the susceptibility phase diagram of consolidated spin ladder compound, C9H18N2CuBr4.