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Transport Behavior and Low Field Magnetoresistance of Polycrystalline La0.63Y0.07Sr0.30MnO3 and La0.

Corresponding Author : M. Nahar (fahimdu@gmail.com)

Authors : Md. D. Rahaman , M.H.R. Khan , A. K. M. Akther Hossain

Keywords : X-ray diffraction, polycrystalline samples, attice mismatch, paramagnetism, ferromagnetism

Abstract :

Polycrystalline manganites of nominal chemical compositions La0.63Y0.07Sr0.30MnO3 and La0.63Y0.07Ba0.30MnO3 sintered at 1673K were investigated to observe transport properties and low field magnetoresistance (MR). XRD measurements confirmed formation of single phase pseudocubic perovskite structure. The temperature dependent DC transport properties showed a metalsemiconductor transition. A giant negative magnetoresistance (GMR) effect is observed at transition temperature in presence of magnetic field; which is mainly attributed to the intrinsic properties of grains and random fluctuation of electron-phonon spin interaction due to phase transition. A large MR is also observed at low temperatures (78-150K) due to unaligned spin orientation and spin polarized tunneling among grain boundaries in ferromagnetic region at very low applied field. It is found that the size of substituted cations and the substitution of Y3+ greatly modify MR sensitivities.  

Published on December 30th, 2012 in Volume 20, Issue 3, Applied Sciences and Technology