Letter. Spin-glass order induced by dynamic frustration

Goremychkin, E.A., Osborn, R., Rainford, B.D., Macaluso, R.T., Adroja, D.T. and Koza, M. (2008) Letter. Spin-glass order induced by dynamic frustration. Nature Physics, 4 (10), 766-770. (doi:10.1038/nphys1028).

Abstract

Spin glasses are systems whose magnetic moments freeze at low temperature into random orientations without long-range order. It is generally accepted that both frustration and disorder are essential ingredients in all spin glasses, so it was surprising that PrAu2Si2, a stoichiometric compound with a well-ordered crystal structure, was reported to show spin-glass freezing. Here, we report on inelastic neutron scattering measurements of crystal-field excitations, which show that PrAu2Si2 has a singlet ground state and that the exchange coupling is very close to the critical value to induce magnetic order. We propose that spin-glass freezing results from dynamic fluctuations of the crystal-field levels that destabilize the induced moments and frustrate the development of long-range magnetic correlations. This novel mechanism for producing a frustrated ground state could provide a method of testing the concept of 'avoided criticality' in glassy systems.

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