Abstract
We have investigated both temperature and magnetic field dependences of the resistivity of Nd0.67Ba0.33Mn0.98Fe0.02O3 perovskite. Electrical-resistivity measurement in the temperature range 5–230 K shows a metal – semiconductor transition at peak temperature, TMS, which shifts to higher temperature when the magnetic field increases. At a field of 7 T the sample presents a large magnetoresistance (MR) effect (∼97%). In 5–40 K temperature range the sample shows a minimum of resistivity, presumably due to the combined effect of weak localization, electron–electron and electron–phonon scattering. In 40–230 K temperature range the resistivity data were well fitted with the phenomenological percolation model, which is based on the phase segregation of ferromagnetic-metallic clusters and paramagnetic-semiconductor regions. The temperature and field dependences of resistivity data, ρ(T, H), allowed us to determine the magnetic entropy change, ΔSM, using the following equation ΔSM=−α∫0H(∂Ln(ρ)/∂T)HdH, which relates the magnetic order to the transport behavior of our sample. Results show that the as obtained magnetic entropy change values are similar to those determined using data obtained from the investigation of temperature and magnetic field dependences of magnetization.
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