Spin Glass Behavior in the Ru-1222 and Ru-1212 rutheno-cuprate families: a comparative study.

Strong ev- idences of a spin glass phase on polycrystalline RuSr2Ln1.5Ce0.5Cu2O10−� (LnRu-1222, Ln = Y, Ho and Dy) is provided by ac susceptibility (�ac) and dc magnetization measurements. The fingerprint of a spin glass transition, the frequency-dependent cusp inac vs. T measurements at low magnetic field, is observed for all LnRu-1222 samples. The change in the cusp position with frequency follows the Vogel-Fulcher law, which is commonly accepted to describe a spin glass with magnetically interacting clusters. The strong supression of the cusp in the ac susceptibility measurement in the presence of magnetic fields as low as 500 Oe, and the results of thermoremanent magneti- zation (TRM) and isothermal remanent magnetization (IRM) measurements