Spin Waves and Spin Glass Effects on a Frustrated Kagome Lattice

Magnetothermal data are presented for the compound SrCr sub 8-x Ga sub 4+x O sub 19, for a wide range of temperature, field, and dilution strengths. Despite a large AF Curie-Weiss temperature of 515 K, the x=O material undergoes a spin glass (SG) transition at only 3.3 K. This is thought to be a result of the combined effects of the quasi-2D structure and frustration within the magnetic planes. Below the SG transition the specific heat displays a quadratic temperature dependence over a wide range of temperature and magnetic ion concentration. This is in sharp contrast to the linear dependence usually observed in conventional SG, and requires introducing a new type of spin-wave-like excitation. A model which incorporates these new excitations and the SG behavior will be discussed.