Influence of cuprate spacer layer on electrical and magnetic properties of La_0.6Pb_0.4MnO₃/La₄BaCu₅O_13+x multilayers

Abstract

The magnetic and transport behavior of the multilayers of ferromagnetic (La_0.6Pb_0.4MnO₃)/nonmagnetic metallic oxide (La₄BaCu₅O_13+x) fabricated on LaAlO₃ (100) substrate by pulsed laser deposition has been investigated. The thickness of the nonmagnetic layer has been varied from 1 unit cell to 8 unit cells while keeping the ferromagnetic layer thickness constant at 10 unit cells, mainly to explore the possible existence of oscillations in the magnetic coupling. Interestingly, the Curie temperature as well as the magnetoresistance decreased monotonically with increasing the spacer layer thickness, in sharp contrast to a recent report on the existence of oscillations in the exchange coupling in another manganite-based multilayer [Phys. Rev. Lett. 85, 3728 (2000)]. The insulator-to-metal transition is found to be suppressed progressively in the multilayers. The application of external magnetic field induces a crossover from two to three dimensions for electrical conductivity. Interestingly, the multilayers exhibit semiconductinglike behavior, though thin films of individual oxides are metallic below 300 K.