Spin glass behavior in metallic pyrochlore ruthenate Ca2Ru 2O7

Abstract

Spin glass properties of a novel ruthenate, Ca2Ru 2O7, were studied by precise magnetization measurements. The effective moment per Ru atom is only 0.25μB, which is one decade smaller than that expected from a localized spin model with S 3/2 for Ru5+. In spite of the small moment, a spin glass transition occurs at Tg 25.0 K, and the nonlinear susceptibility χnl( χ2) diverges negatively at Tg. The value of the critical exponent δ can be estimated as δ 3.7 from the magnetic field dependence of χnl at Tg, which is compared to those of other pyrochlore spin glasses and the canonical spin glasses. © 2009 IOP Publishing Ltd.