Spin dynamics of the director state in frustrated hyperkagome systems

Abstract

We present an experimental study of the magnetic structure and dynamics of two frustrated hyperkagome compounds, Gd 3 Ga 5 O 12 and Gd 3 Al 5 O 12 . It has previously been shown that Gd 3 Ga 5 O 12 exhibits long-range correlations of multipolar directors that are formed from antiferromagnetic spins on loops of ten ions. Using neutron diffraction and reverse Monte Carlo simulations we prove the existence of similar magnetic correlations in Gd 3 Al 5 O 12 , showing the ubiquity of these complex structures in frustrated hyperkagome materials. Using inelastic neutron scattering we shed further light on the director state and the associated low-lying magnetic excitations. In addition, we have measured quasielastic dynamics that show evidence of spin diffusion. Finally, we present AC susceptibility measurements on both Gd 3 Ga 5 O 12 and Gd 3 Al 5 O 12 , revealing a large difference in the low-frequency dynamics between the two otherwise similar compounds.

An Overview of the Director State in Gadolinium Gallate Garnet

“…Recent results on the isotructural compounds Gd 3 Al 5 O 12 and Yb 3 Ga 5 O 12 reveal that the director state in GGG is not unique [20,33,34]. All three compounds reveal a broad feature in the temperature dependence of the specific heat as a precurser to a longer ranged ordered state.…”