Magnetic and electronic properties of charge ordered Nd0.8Na0.2MnO3

Abstract Nd 0.8 Na 0.2 MnO 3 polycrystalline ceramic is prepared by sol–gel method and its magnetic properties, electron spin resonance spectra and electronic transport properties have been investigated experimentally. Above 155 K, the compound is a paramagnetic insulator. As the compound is cooled from room temperature, a charge-ordered state first develops below 155 K. Above 110 K, the resistivity data follow the variable-range hopping model, and an abrupt reduction in the localization length is observed around charge ordering temperature. Below 110 K, the compound tends to be intrinsically inhomogeneous, i.e., ferromagnetic metal components and paramagnetic insulator domains coexist in this system at zero field. Below 40 K, the fractions of ferromagnetic metal components exceed the percolation threshold value and the compound shows a metallic behavior. When a magnetic field with magnitude of 140 kOe is applied, the charge-ordered state is melted and only a paramagnetic insulator to ferromagnetic metal transition is observed over the whole measured temperature range.