Dilution-Enhanced Spin Glass Ordering from Frustration in SrCr sub (8-x) Ga sub (4+x) O sub (19).

The magnetic interactions in SrCr sub 8 Ga sub 4 O sub (19) are highly frustrated. Magnetization and specific heat data are presented and show the existence of paramagnetic-to-spin glass ordering but only at T sub f = 3.5K, despite the high Curie-Weiss temperature of 515K. Several other unusual properties are found, including an inverse relationship of ordering temperature to magnetic ion concentration for a set of different-size crystals. This result is conjectured to arise from the competition between frustration on a modified Kagome lattice and a tendency toward three-dimensional order, controlled by preferential site substitution.