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Enhanced low‐field magnetoresistance of La 0.7 Sr 0.3 Mn 1– x Ni x O 3 compounds by annealing process
Author(s) -
Ahmed A. M.,
Abedellateef M. A.,
Abd ElGhanny H. A.,
Mohamed Abd El Mo'ez A.
Publication year - 2015
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201431556
Subject(s) - magnetoresistance , annealing (glass) , electrical resistivity and conductivity , seebeck coefficient , condensed matter physics , variable range hopping , materials science , polaron , atmospheric temperature range , doping , crystallite , magnetic field , thermal conduction , physics , metallurgy , electron , thermodynamics , quantum mechanics , composite material
A study of Mn‐site substitution by Ni 2+ and the effect of annealing time in polycrystalline bulk La 0.7 Sr 0.3 MnO 3 in composition range (0 ≤ x ≤ 0.1) is presented. This study involves structural, electrical, magnetoresistance, and thermoelectric power (TEP) measurements. X‐ray diffraction was used to examine the structure for the as‐prepared and annealed samples, and it shows that there is no change in structure with annealing time. Electrical resistivity and magnetoresistance are strongly affected by annealing process, where there is a dramatic increase in resistivity with annealing time and an enhancement in magnetoresistance in different temperature ranges. Moreover, conduction mechanisms above and below transition temperature ( T ms ) are discussed, since, variable‐range hopping and small‐polaron hopping models are applied above T ms , in addition to some experimental relations below it. In addition, the TEP sign changes from positive to negative with doping and annealing.