Epitaxial variant structures of the perovskite manganites with the high tunnel magnetoresistance

We have found that single-crystal substrates of ZrO2(Y2O3) with (0 0 1) and (1 1 1) orientation are suitable for the growth of (1 1 0) perovskite films of La0.7Ca0.3MnO3, La0.7Sr0.3MnO3 and La1-xMnO3 (x=0.1-0.25) with the in-plane variant structure. The orientation types and crystallographic domains were determined by X-ray diffraction and high-resolution TEM. Special high-angle boundaries formed between the nanodomains of the epitaxial variants result in the high tunnel magnetoresistance (above 15% at 77K and 0.1 T). The magnetic reversal transition was also detected in the field below 0.01 T, the sharpness of the transition was found to be very sensitive to the film microstructure. Further enhancement of the magnetoresistance was achieved in the heterostructures including perovskite manganite and ferrimagnetic insulating oxide layers. (C) 2004 Elsevier B. V. All rights reserved.