Transition temperature of three-dimensional quantum Heisenberg ferro- and antiferromagnets

The transition temperature between the ordered and the paramagnetic phase of 3D quantum Heisenberg ferro- and antiferromagnets is theoretically predicted with very good accuracy for any spin value, starting from its known counterpart for the classical system. The really straightforward evaluation is made possible by a method that reduces the quantum problem to an e!ective classical Hamiltonian.