Magnetotransport properties of ferromagnetic LaMnO3+ δ nano-sized crystals

Abstract: Transport and magnetic properties of LaMnO3+ δ nanoparticles with average size of 18nm have been investigated. The ensemble of nanoparticles exhibits a paramagnetic to ferromagnetic (FM) transition at T C∼246K, while the spontaneous magnetization disappears at T≈270K. It was found that the blocking temperature lies slightly below T C. The temperature dependence of the resistivity shows a metal–insulator transition at T≈192K and low-temperature upturn at T<50K. The transport at low temperatures is controlled by the charging energy and spin-dependent tunnelling through grain boundaries. The low temperature I–V characteristics are well described by indirect tunnelling model while at higher temperatures both direct and resonant tunnelling dominates. [Copyright &y& Elsevier]