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The interactions in the magnetoplumbite isomorph SrCr₈Ga₄O₁₉ are highly frustrated. Thermodynamic data are presented and show the existence of a transition from paramagnetic to spin-glass ordering but only at T₂=3. 3 K, despite the high Curie-Weiss temperature of 515 K. Other unusual properties include a low-temperature specific heat varying as T^2 and an inverse relationship of T₂ to magnetic-ion concentration for a set of differently prepared crystals. This result is conjectured to arise from competition between 2D frustration and a tendency toward 3D order, controlled by preferential site substitution.
Ramirez et al. (Mon,) studied this question.