Strain-controlled anisotropic electronic transport in Bi_0.4Ca_0.6MnO₃ films

Structural and resistive anisotropy has been studied for the Bi_0.4Ca_0.6MnO₃ films grown on (011)-oriented SrTiO₃ substrates. Strong anisotropic transport behaviors are observed when significant lattice strains exist. The ratio of the two resistivities along the a and c axes of the films can be tuned between ∼1 and ∼13 by adjusting the a/c ratio between ∼1.01 and ∼1.04, which can be conducted simply by decreasing film thickness from 100 to 10 nm. Considerable anisotropy emerges and develops when film thickness drops below ∼60 nm. With the decrease in film thickness, a change in preferred growth direction of the films is also observed. These features of the lattice effects could be useful for the design of artificial materials and devices. © 2008 American Institute of Physics.