Open AccessCrystallization Dynamics and Magnetoresistance of La0.7Ca0.3MnO3 Synthesized by Mechanical Alloying
Author(s) -
Jin Zhiqiang,
Qin Hong-Xia,
JianRong Zhang,
Dunhui Wang,
Youwei Du
Publication year - 1999
Publication title -
wuli xuebao
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.199
H-Index - 47
ISSN - 1000-3290
DOI - 10.7498/aps.48.230
Subject(s) - magnetoresistance , materials science , crystallization , curie temperature , annealing (glass) , amorphous solid , activation energy , condensed matter physics , electrical resistivity and conductivity , phase (matter) , colossal magnetoresistance , perovskite (structure) , thermodynamics , ferromagnetism , crystallography , chemistry , magnetic field , metallurgy , physics , organic chemistry , quantum mechanics
Pure, single-phase La0.7Ca0.3MnO3 perovskites with giant magnetoresistance effect have been successfully prepared by mechanical alloying. The amorphous phase formed in milled smples transforms at about 920K into perovskite-type phase. Following the law of mass action, crystallization dynamics of the amorphous phase has been discussed. The activation energy for crystallization transformation is calculated to be about 265kJ/mol. The characterization of resistivity ρ(T) for La0.7Ca0.3MnO3 perovskites has also been investigated. At low temperatures T, ρ(T) has a directproportion dependence on T2. With increasing annealing temperature, the slope of ρ-T2 curve decreases. The temperature dependent magnetoresistance effect at temperatures far below the Curie temperature can be well expressed by the equation Δρ/ρ0=p1-p2T3/2-p3T5/2.