Magnetorresistence and magnetic behavior of manganite-based multilayers

M. SIRENA,; M. GRANADA,; N. HABERKORN,; L. STEREN; J. GUIMPEL

Denver, Colorado (USA)

Simposio; Magnetic Interfaces and Nanoestructures. AVS 49th International Symposium; 2002

American Vacuum Society

  We have studied the physical and structural properties of multilayers based on manganite compounds. Different ferromagnetic (FM) spacers, insulator (B1) and metallic (B2), have been used in order to compare the magnetoresistance (MR) effects and interlayer coupling of both kind of systems. Multilayers based on high polarized manganites are specially interesting for developing magnetic devices with high tunneling MR, spin filters, etc. A/B1 and A/B2 multilayers (A: La0.55Sr0.45MnO3, B1: La0.9Sr0.1MnO3 and B2: La0.67Ca0.33MnO3) have been grown by DC sputtering on MgO and SrTiO3 substrates. X-ray diffraction patterns have been fitted to obtain information about the interface and roughness interdiffusion. The results show that the samples grow strongly textured in the c-direction, perpendicular to the sample surface, with a multilayered structure. The similar structure and lattice parameters of the samples make these films specially attractive to build multilayers with interfaces of good quality. We have studied the dependence of the transport and magnetic properties of these systems with the interlayer and top-layer thickness. Both A/B1(B2)/A trilayers present properties similar to those observed for the La0.55Sr0.45MnO3 film. Magnetization vs. field measurements performed in both systems, show a single FM loop indicating that the A layers are always ferromagnetically coupled. The FM nature of the interlayer in the A/B1/A case is probably the origin of the FM coupling. In the A/B2/A trilayers, on the other hand, the FM coupling above its Curie temperature could be mediated by short-range ordered zones in the LaCaMnO interlayer. No extrinsic MR, associated with the multilayered structure was observed in the whole temperature range, probably due to the presence of FM coupling between the metallic layers, as suggested by magnetization measurements.