Spin glass order induced by dynamic frustration

Inelastic neutron scattering from PrAu2Si2

Inelastic neutron scattering from PrAu2Si2 measured at 1.5 K on HET with an incident energy of 18 meV. The solid line is the result of a fit to a crystal field model, with the individual crystal field transitions displayed as dashed lines. The shaded area is the phonon scattering estimated from data taken at high scattering angle.
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Spin glasses (SG) are systems whose magnetic moments freeze at low temperature into random orientations

The presence of frustration and disorder are necessary ingredients for an SG transition. It was therefore surprising that PrAu2Si2 was reported to show all the characteristics of a SG, even though it is a stoichiometric compound with a well-ordered structure. To understand the origin of the SG ground state in PrAu2Si2, we have performed inelastic neutron scattering measurements of the crystal field (CF) excitation spectrum. These measurements classified PrAu2Si2 as an induced moment SG where the exchange interaction is only just above the critical value for induced moment magnetism with substantial CF linewidth at Tg which plays a central role in disrupting of induced moment formation (see figure) and resulting in the SG ground state. We suggest that PrAu2Si2 reveals a new way to achieving frustration in systems with neither static disorder nor geometrically frustrated lattices, through dynamic fluctuations in proximity to a critical phase boundary.

EA Goremychkin, DT Adroja (ISIS), R Osborn (ANL, USA), B Rainford (University of Southampton), M Koza (ILL, France)

Research date: December 2007

Further Information

EA Goremychkin et al, J. Mag. Mag. Mat. 310 (2007) 1535

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