Crystal structure and magnetoresistance of Na-doped LaMnO3

The crystal structure and magnetoresistance of La1-xNaxMnO3 (0.05 less than or equal to x greater than or equal to 0.20) are investigated. La1-xNaxMnO 3 crystallizes in a rhombohedrally distorted perovskite structure and exhib its a sharp ferromagnetic transition as well as a negative magnetoresistanc e at around room temperature. On the basis of alternating-current susceptib ility and resistivity measurements as well as a comparison with La1-xSrxMnO 3 compounds, it is proposed that Na doping tends to drive the system from a regime characterized by strong Hund coupling and strong electron-phonon co upling to one characterized by weak Hund coupling and weak electron-phonon coupling.