Low-field magnetoresistance of La_(0.7)Ca_(0.3)Mn0_3 perovskite synthesized byreactive milling method

摘要

Nanocrystalline, granular samples of La_(0.7) Ca_(0.3)Mn0_3 (LCMO) were synthesized by reactive milling methodand annealed at various temperatures. Effect of grain size on the low-field magnetoresistance (LFMR) hasbeen investigated. Based upon a phenomenological model taking into account the spin-polarized trans-port across grain boundaries, we explained magnetic field dependence of magnetoresistance in LCMOsamples. The contribution to the magnetoresistance coming from spin-polarized tunneling was separatedout from the intergranular contribution. The fitted results showed that the temperature dependence of the LFMR displays a Curie-Weiss law-like behavior.