Abstract
The effect of Fe doping (less than or equal to 10%) on polycrystalline
samples of La0.7Sr0.3MnO3 has been studied through X-ray diffraction.
resistivity, AC susceptibility, magnetization, and magneto resistance
measurements. Fe doping was found to change substantially the magnetic
and transport properties of the samples, without modifying the lattice
structure. In a magnetic field of 5 T, the magnetoresistance of a sample
doped with 10% Fe was 4 times greater than that of an undoped sample,
near the resistivity peak. This result was explained in terms of the
formation of antiferromagnetic clusters of Fe ions. Magnetoresistance
did not depend on Fe doping at 5 K, but there was a large
magnetoresistive effect in fields less than 0.5 T in all samples. This
behavior was attributed to spin polarized tunneling at grain boundaries
of polycrystalline samples. (C) 2001 Published by Elsevier Science B.V.
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