Here we report an unconventional magnetic and transport phenomenon in a layered cobalt oxide NaxCoO2. Only for x = 0.75, a magnetic transition of the second order was clearly detected at Tm ∼22 K where an apparent specific-heat jump, an onset of extremely small spontaneous magnetization, and a kink in resistivity came in. Moreover large positive magnetoresistance effect was observed below Tm. These features of the transition strongly indicate the appearance of an unusual electronic state that may be attributed to the strongly correlated electrons in Na0.75CoO2.
|Number of pages||5|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 1 Feb 2003|
|MoE publication type||A1 Journal article-refereed|