Electrical resistivity and enhanced magnetoresistance in (La0.6Pb0.4MnO3/La0.85MnO3−δ)n superlattices

Abstract
Resistivity and magnetoresistance studies have been carried out on (La0.6Pb0.4MnO3/La0.85MnO3−δ)n (n=30 periods) ferromagnetic/paramagnetic oxide multilayers fabricated by pulsed laser deposition. An epitaxial film of La0.6Pb0.4MnO3 is ferromagnetic and metallic below 320 K, whereas that of La0.85MnO3−δ is a paramagnetic (and antiferromagnetic at low temperatures) insulator. The multilayers showed an insulator-to-metal transition at 285±5 K. The magnetoresistances of these multilayers were about 60%–75% at the transition temperature in 6 T magnetic field. The magnetoresistance is also shown to be dependent on the thickness of the ferromagnetic oxide layer. A maximum magnetoresistance of 75% was observed for a [La0.6Pb0.4MnO3(50 Å)/La0.85MnO3−δ(20 Å)]30 superlattice as against 25% in a single La0.6Pb0.4MnO3 film at 285 K.