摘要
La_(0.67)Ca_(0.33)MnO_3)_x /(ZrO_2)_(1-x) (x is the volume fraction ratio) percolated composites were fabricated by combining La_(0.67)Ca_(0.33)MnO_3 (LCMO) powders with ZrO_2 particles, where LCMO powders were prepared by sol-gel process. Low field magnetoresistance ( LFMR ) is greatly enhanced at low temperature when the system is close to the metallic percolation threshold of x=0.4. The magnetoresistance ratio of ( LCMO)_(0.4) /( ZrO_2 )_(0.6) in a 10 mT magnetic field at 77 K is 7.8 %, about 7.12 times larger than that of pure LCMO compound. The enhancement of spin-dependent tunneling of electrons at the interfaces between LCMO and ZrO_2 grains is responsible for the enhanced LFMR. With increasing ZrO_2 addition, Curie temperature T_C decreases firstly and then remains constant at about 220 K when (x<60%), showing limited substitution effect of Zr ions on B sites.
La_(0.67)Ca_(0.33)MnO_3)_x /(ZrO_2)_(1-x) (x is the volume fraction ratio) percolated composites were fabricated by combining La_(0.67)Ca_(0.33)MnO_3 (LCMO) powders with ZrO_2 particles, where LCMO powders were prepared by sol-gel process. Low field magnetoresistance ( LFMR ) is greatly enhanced at low temperature when the system is close to the metallic percolation threshold of x=0.4. The magnetoresistance ratio of ( LCMO)_(0.4) /( ZrO_2 )_(0.6) in a 10 mT magnetic field at 77 K is 7.8 %, about 7.12 times larger than that of pure LCMO compound. The enhancement of spin-dependent tunneling of electrons at the interfaces between LCMO and ZrO_2 grains is responsible for the enhanced LFMR. With increasing ZrO_2 addition, Curie temperature T_C decreases firstly and then remains constant at about 220 K when (x<60%), showing limited substitution effect of Zr ions on B sites.
基金
ProjectsupportedbyStateKeyProjectofFundamentalResearch(19980613010)andtheNaturalScienceFoundationof WeifangUniversity(2005202)
