Dimensional crossover and anomalous magnetoresistivity in single crystals NaₓCoO₂

الأصل · EN

The in-plane (ρab) and c-axis (ρc) resistivities, and the magnetoresistivity of single crystals NaₓCoO₂ with x = 0.7, 0.5 and 0.3 were studied systematically. ρab(T) shows similar temperature dependence between Na₀.₃CoO₂ and Na₀.₇CoO₂, while ρc(T) is quite different. A dimensional crossover from two to three occurs with decreasing Na concentration from 0.7 to 0.3. The angular dependence of in-plane magnetoresistivity for 0.5 sample shows a "d-wave-like" symmetry at 2K, while the "p-wave-like" symmetry at 20 K. These results give an evidence for existence of a spin ordering orientation below 20 K turned by external field, like the stripes in cuprates.