Magnetically ordered phase of sodium cobalt oxyhydrate

Abstract In order to elucidate the x – s – T phase diagram ( s : the Co valence and T : temperature) of the sodium cobalt oxyhydrate, Na x (H 3 O) z CoO 2 · y H 2 O, a magnetically ordered phase ( M phase) in the system is investigated by measuring magnetization curves of samples with three chemical compositions. The M phase is located at the range of 0.33 x s =+3.40 section, and it seems to shift slightly to the lower x direction with increase in s . On s =+3.48 section, the M phase appears around x =0.33 under high magnetic field.