Magnetic interactions and short range order in gadolinium gallium garnet

Previous studies of gadolinium gallium garnet (GGG) have indicated relatively strong antiferromagnetic interactions but, somewhat surprisingly, no evidence of long range magnetic order at temperatures down to 0.35 K. To understand this behavior, we have measured the non-dipolar interactions between first, second and third nearest neighbors, using an improved high frequency relaxation method, and we have combined the results in a Monte Carlo computer simulation to calculate the thermal properties. General agreement with the earlier specific heat measurements is obtained and it is concluded that the broad peak observed near 0.8 K is due to short range order resulting from ’’frustration’’ caused by the unusual structure of the garnet lattice.