1204.2559 (L. Isaev et al.)

Frustrated magnets and quantum paramagnetic phases at finite temperature    [PDF]

L. Isaev, G. Ortiz

We develop a general framework, which combines exact diagonalization in small clusters with a density matrix variational principle, to study frustrated magnets at finite temperature. This thermodynamic hierarchical mean-field technique is used to describe the phase diagram and magnetization process of the 3D spin-1/2 $J_1$-$J_2$ antiferromagnet on a stacked square lattice. We demonstrate that with temperature the non-magnetic region of this model exhibits a crossover from quantum to classical paramagnet, and show how the corresponding temperature scale can be extracted from thermodynamic measurements. Below this crossover temperature an applied magnetic field induces a variety of phases with non-trivial spin textures. We discuss implications of our results for experiments in frustrated vanadium oxides.

View original: http://arxiv.org/abs/1204.2559