Observation of Spin-Glass Behavior in La0.85Sr0.15CoO3 Single Crystals

The magnetic behavior of La0.85Sr0.15CoO3 single crystals and polycrystals has been subjected to a controversial debate for the last several years; while some groups show evidence for phase separation, others show spin-glass (SG) behavior. Here, we present a comprehensive investigation of the structural, ac susceptibility, and dc magnetization properties of La0.85Sr0.15CoO3 single crystals grown by float zone method. The structural analysis of XRD data by Rietveld refinement reveals the single crystallographic phase. The ac susceptibility results exhibit a frequency dependent peak shift (similar to similar to 2 K) and time-dependent memory effect below the freezing temperature. The characteristic time scale tau (o) calculated from this peak shift is found to be of similar to 10(-13) s which matches very well with typical values observed for a SG system. Further, the peak shift of the zero-field-cooling curves to lower temperature at higher dc fields is well described by the well-known de Almeida Thouless line, a characteristic of SG behavior. Thus, all our experimental findings confirm the existence of SG behavior in La0.85Sr0.15CoO3 single crystals.