Enhancement of the magnetoresistive effect in nanocomposites based on manganite La_0.67Sr_0.33MnO₃ and magnetite Fe₃O₄

The effect of a magnetite Fe₃O₄ nanopowder in a nanocomposite with manganite La_{0. 67}Sr_{0. 33}MnO₃ on its magnetoresistive effect and conductivity is studied. The addition of a magnetite nanopowder to the initial material leads to a substantial (twofold) increase in the low-field magnetoresistive effect. The low-field magnetoresistive effect in substituted lanthanum manganite nanopowders is based on spin-dependent electron tunneling through grain boundaries. The transport mechanisms in such systems are analyzed, and noise spectroscopy is also used for this purpose.