Metal–insulator transition and hopping conduction mechanisms in the La0.7Ba0.3MnO3 compound

The La0.7Ba0.3MnO3 compound, obtained in volume by sol–gel with a cubic crystal lattice, exhibits metal–insulator phase transitions near 336 K and a ferromagnetic–paramagnetic transition near 375 K. The correlation between the magnetic and transport properties is evidenced by AC susceptibility measurements, impedance spectroscopy and DC conductivity. The activation energy values obtained by impedance spectroscopy and by the four-point method differed slightly. The real part of the conductivity σ′(ω) for different temperatures showed a plateau (DC regime) for various frequency decades followed by a dispersive region following a Jonscher's power law tendency. The value of the exponent n, which was less than one, showed a distribution of relaxation times. The cross-frequency ωp, which was associated with the carrier hopping frequency, showed a thermally activated tendency with an almost constant carrier density for the entire range of temperatures. The relaxation time distribution was also verified by the dielectric modulus M(ω). - Highlights: ► La0.7Ba0.3MnO3 compound have been prepared and characterized. ► La0.7Ba0.3MnO3 compound exhibits metal–insulator phase transitions near 375 K and a ferromagnetic–paramagnetic transition near 336 K. ► The activation energy values obtained by impedance spectroscopy and by the four-point method differed slightly. ► The conductivity real part showed a plateau (DC regime) followed by a dispersive region following a Jonscher's power law. ► La0.7Ba0.3MnO3 showed a distribution of relaxation times