Muon spin relaxation investigation of frustrated antiferromagnetic pyrochlores A2B2O7

In a system where magnetic ions occupy the vertices of edge or corner sharing triangular units, the natural antiferromagnetic coupling between ions is geometrically frustrated. A wide variety of interesting magnetic behaviour has been observed in pyrochlores, where magnetic ions form a network of corner sharing tetrahedra. The low temperature spin dynamics of a number of pyrochlores A2B2O7 have been investigated using the technique of μSR. For example, Y2Mo2O7 shows a transition to a disordered magnetic state similar to a spin glass at TF = 22 K. However, unlike conventional metallic spin glasses, a non-zero muon spin depolarization rate is observed to persist well below 0.1 TF. These results suggest that there is a finite density of states for magnetic excitations in this system near zero energy.