The low-field magnetoresistance of La 0.7 Ca 0.3 MnO 3 films deposited on different substrates has been measured. Whereas post-annealed films on SrTiO 3 and LaAlO 3 exhibit a clear anisotropic magnetoresistance (AMR), the low-field magnetoresistance of as-deposited films on LaAlO 3 and Si is dominated by grain-boundary magnetoresistance. At low temperatures the anisotropic magnetoresistance is temperature independent with a value of about −0.2 ± 0.1%. A simple atomic d-state model can explain the sign of the anisotropic magnetoresistance.
La 0.7 Ca 0.3 MnO 3 films with thicknesses between 2 and 300 nm were fabricated on LaAlO3, SrTiO3, and (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) substrates using pulsed laser deposition. After annealing at 950 °C in flowing oxygen, on LaAlO3 and LSAT, strain-relaxed epitaxial films of high quality were obtained. The magnetization, resistivity, and magnetoresistance of the films was studied as a function of thickness. Down to a thickness of about 4 nm no decrease of the saturation magnetization could be detected; the Curie temperature decreases slightly with thickness in agreement with finite size scaling theory. The thickness dependence of the conductance can be understood as a size-effect in thin films; there is no indication of an electrically dead interfacial layer.
Thin-films of magnetite, F@04 have been produced by the XeCl excimer laser ablation of both Fe304 and metallic Fe targets. The ablation of metallic Fe has been shown to produce about two orders of magnitude smaller concentration of boulders than the ablation of bulk magnetite. The use of single-crystal, latticematching substrates was found to be necessary at lower fluences (1 -3 J c m -' ) for the ablation of metallic Fe, whereas polycrystalline, non-latticematching substrates were adequate for deposition with moderate laser fluences (5 -6 J cm") Film quality, which has been assessed by examining the
A new high quality joining technique of melt processed YBCO has been developed based on interfacial melting induced by a metallic silver foil inserted between two single domain YBCO tiles. This simple technique allows joining large monoliths to form the complex-shaped pieces required for many power applications. Hall probe magnetic flux profile analysis under magnetic field and high field magnetoresistance measurements demonstrate that the superconducting behaviour of the joint is indistinguishable from the bulk.
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