Low Temperature Anomalies in the Specific Heat and Magnetic Susceptibility of Na_(0.7)CoO_2 Samples

摘要

We present a comparative study of Na_(0.7)CoO_2 samples obtained from three different sources and prepared by different methods. The specific heat and magnetic susceptibility measurements in the temperature range 2-300 K show substantial influence on the observed anomalies, which underlines that the system is extremely sensitive to preparation protocols.