Extrinsic Magnetotransport in Manganites and its Dependence on Mechanical Strain (eBook)

Ramesh Babu (Autor)

eBook Download: PDF

2008 | 1. Auflage
106 Seiten
Cuvillier Verlag
9783736927810 (ISBN)

Infos

The extrinsic electrical transport in manganites of the type (La,A)(Mn,B)O3 (where A = Ca2+, Sr2+ or Pb2+ and B = Ru+, Ta+ or W+) has been studied on bulk ceramic and thin film samples. In particular, its dependence on reversible strain applied with a piezoelectric substrate has been investigated. The first part discusses results on bulk polycrystalline samples, (La0.7Ca0.3MnO3)/LaAlO3 (001) films forming step edge junctions (SEJ) on substrates containing lithographically defined parallel steps and La0.7Sr0.3MnO3/SrTiO3 (001) films on a bicrystal substrate containing one grain boundary. Magnetoresistance measurements have been carried out in static and in pulsed magnetic fields of μ0H = 50 T. The magnetoconductance G(H) depends on the susceptibility of a magnetically less ordered layer around the grain boundaries. In particular, the second-order grain boundary tunnelling model of Lee et al. [Lee 99] is employed to discuss the magnetoconductance data. The bulk ceramic samples of various compositions and a polycrystalline La0.7Sr0.3MnO3 film show dominating antiferromagnetic interactions in the grain boundary layer, whereas spin-glass-like disorder is concluded from transport data for the (La0.7Ca0.3MnO3)/LaAlO3 (001) SEJ. The bicrystal transport behaviour appears dominated by a small number of magnetic domains next to the bicrystal grain boundary. The second part of this work addresses the influence of a reversible strain on electrical grain boundary transport. The strain is applied through a piezoelectric pseudocubic substrate of PMN-PT (001) to the films. In detail, polycrystalline films, films grown on substrates with parallel steps of several 100 nm height and a film on a substrate containing an intentionally applied scratch were investigated. Large strain response of the junction resistance and the magnetoresistance has been observed for the SEJ films, with strong dependence on the film thickness, and is discussed within the indirect tunnelling model (mentioned above). Polycrystalline films showed a more moderate strain effect.

Produkt-Details

• Erscheint lt. Verlag: 16.10.2008
• Sprache: englisch
• Themenwelt: Mathematik / Informatik ► Mathematik
• ISBN-13: 9783736927810 / 9783736927810