Monte Carlo studies of +or-J spin glasses with continuous symmetries in D=2

The authors have calculated the internal energy, specific heat and susceptibility chi of random +or-J planar and Heisenberg magnets in two dimensions. In the Heisenberg model, chi is Curie-like at all temperatures studied. By contrast, the planar model chi decreases at the lowest temperatures, and increases strongly with increasing sample size at temperatures from (0.5-1)J. These results are compared with theoretical predictions for model systems with frustration and disorder.