Study of magnetic and magnetoresistance behaviour of La0.67Sr0.33MnO3-CoFe2O4 composites

Abstract Nanocomposites of Lanthanum Strontium Manganite and Cobalt Ferrite with different weight percentages were prepared using the sol-gel method and sintered at 950 °C. Presence of constituent phases of La 0.67 Sr 0.33 Mn O 3 and CoFe 2 O 4 peaks were confirmed from X-ray diffraction and Fourier transform infrared spectroscopy studies. Hysteresis behaviour shows room ferromagnetism for the composite samples and their variation in saturation magnetization can be understood on the basis of competing effects between both the magnetic phases. Enhancement of squareness ratio and coercivity indicate the strengthening of exchange-coupling interaction due to closer proximity of hard and soft phases. Metallic state vanishes and resistivity increases with the incorporation of cobalt ferrite into lanthanum strontium matrix. An enhanced magnetoresistance in a wide temperature range is observed for 25% cobalt ferrite added sample and is ascribed to spin-polarized tunneling mechanism. Adiabatic small polaron hopping mechanism is used to explain the resistivity of the composites in the high temperature region.