Staggered field-induced tricritical behavior in theS=12quasi-one-dimensional Ising antiferromagnet on a stacked triangular lattice: Monte Carlo simulations

Abstract

The impact of a staggered magnetic field due to quantum exchange mixing in the $S=\frac{1}{2}$ quasi-one-dimensional Ising antiferromagnet on a stacked triangular lattice is shown to induce a crossover from $XY$ to tricritical universality at the phase transition to the partially disordered state. Using a unique combination of histogram and cluster heat-bath techniques, extensive Monte Carlo simulations are performed to explore the effects of a small applied field that emulates a previously proposed addition to the spin Hamiltonian formulated to account for unusual spin soliton excitations in such systems. It is argued that quantum fluctuations governing short-range order in low-dimensional frustrated spin systems generally can affect measured critical properties at the onset to long-range magnetic order. Our results explain recent high resolution neutron scattering data on $\mathrm{Cs}\mathrm{Co}{\mathrm{Br}}_{3}$.