Universal Neel Temperature in Three-Dimensional Quantum Antiferromagnets
  We study three-dimensional dimerized S=1/2 Heisenberg antiferromagnets, using quantum Monte Carlo simulations of systems with three different dimerization patterns. We propose a way to relate the N\'eel temperature T_N to the staggered moment m_s of the ground state. Mean-field arguments suggest that T_N is proportional to m_s close to a quantum-critical point. We find an almost perfect universality (including the prefactor) if T_N is normalized by a proper lattice-scale energy. We show that the temperature T* at which the magnetic susceptibility has a maximum is a good choise, i.e., T_N/T* versus m_s is a universal function (also beyond the linear regime). These results are useful for analyzing experiments on systems where the spin couplings are not known precisely, e.g., TlCuCl3. 
Songbo Jin, Anders W. Sandvik
cond-mat.str-el