Low Temperature Spin Dynamics of the Geometrically Frustrated Antiferromagnetic Garnet Gd3Ga5O12

The low temperature spin dynamics of the geometrically frustrated antiferromagnet Gd 3Ga 5O (12) (GGG) have been investigated using muon spin relaxation. No evidence for static order is seen down to a temperature of 25 mK or a few percent of the Curie-Weiss temperature. Instead there is a linear decrease in the Gd spin fluctuation rate below 1 K which extrapolates to a small but finite value of 2 GHz at zero temperature. In terms of the spin fluctuations the system appears essentially to remain dynamic at low temperatures (T>0.02 K) and magnetic fields up to 1.8 T.