Anisotropic magnetoresistance in charge-orderedNa0.34(H3O)0.15CoO2: Strong spin-charge coupling and spin ordering

Abstract

Angular-dependent in-plane magnetoresistance (AMR) for single crystal ${\mathrm{Na}}_{0.34}{({\mathrm{H}}_{3}\mathrm{O})}_{0.15}\mathrm{Co}{\mathrm{O}}_{2}$ with charge ordering is studied systematically. The anisotropic magnetoresistance shows a twofold symmetry at high temperature with rotating $H$ in the Co-O plane, with a sixfold symmetry below a certain temperature $({T}_{\ensuremath{\rho}})$. In the meantime (below ${T}_{\ensuremath{\rho}}$), the positive MR arms are developed in AMR with a rotating magnetic field $(H)$ in the plane consisting of the current and $c$ axis. The variation of AMR symmetry with temperature arises from the subtle changes of the spin structure. These results provide direct evidence for the itinerant electrons directly coupled to the localized spins.