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MA: Fachverband Magnetismus

MA 11: Magnetic Thin Films I

MA 11.6: Talk

Tuesday, March 27, 2007, 11:30–11:45, H10

In-situ strain effect on extrinsic magnetotransport in polycrystalline and ste-edge-junction manganite films — •Ramesh Babu Gangineni, Kathrin Dörr, Konstantin Nenkov, Ingolf Mönch, and Ludwig Schultz — IFW, Dresden, Germany

Grain boundaries and step-edge junctions in ferromagnetic manganites La_0.7A_0.3MnO₃ (A = Sr; Ca) typically act as tunnel junctions for the spin-polarized transport. Variable biaxial strain applied to such a manganite sample may affect the tunnel transport, additionally to the intra-grain effect. Thin polycrystalline films of La_0.7A_0.3MnO₃ (A = Sr; Ca) have been grown by Pulsed Laser Deposition on YMnO₃ - buffered piezoelectric PMN-PT(001) substrates. Films containing step- edge junctions were grown on PMN-PT(001) substrates with etched, 600 nm high parallel steps. Magnetization measurements characterize the magnetic behaviour of the film volume. Electrical resistance has been recorded in dependence on in-situ applied reversible biaxial strain at selected temperatures, temperature and magnetic field. Favourably from practical viewpoint, the strain response of polycrystalline films is typically much less temperature-dependent than that of epitaxial films. A step-edge-junction film of La_0.7Sr_0.3MnO₃ shows huge (gauge factor) G values (of up to 400) in a wide temperature range and associated reduction of resistance and magnetoresistance upon piezoelectric in-plane compression of the film. Relations of microstructure, electric transport mechanism and strain effect will be discussed.