Low temperature tunneling magnetoresistance on (La,Sr)MnO{sub 3}/Co junctions with organic spacer layers

Journal Article · Thu May 01 00:00:00 EDT 2008 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.2924435· OSTI ID:21137245

Vinzelberg, H; Schumann, J; Elefant, D; Gangineni, R B; Thomas, J; Buechner, B ^[1]

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1. Leibniz Institute for Solid State and Materials Research Dresden, IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany)

This paper concerns with giant magnetoresistance (MR) effects in organic spin valves, which are realized as layered (La,Sr)MnO{sub 3} (LSMO)-based junctions with tris-(8, hydroxyquinoline) aluminum (Alq{sub 3})-spacer and ferromagnetic top layers. The experimental work was focused on the understanding of the transport behavior in this type of magnetic switching elements. The device preparation was carried out in an ultrahigh vacuum chamber equipped with a mask changer by evaporation and sputtering on SrTiO{sub 3} substrates with LSMO stripes deposited by pulsed laser technique. The field and temperature dependences of the MR of the prepared elements are studied. Spin-valve effects at 4.2 K have been observed in a broad resistance interval from 50 {omega} to M{omega} range, however, without systematic dependence on spacer layer thickness and device area. In some samples, the MR changes sign as a function of the bias voltage. The observed similarity in the bias voltages dependences of the MR in comparison with conventional magnetic tunnel junctions with oxide barriers suggests a description of the found effects within the classical tunneling concept. This assumption is also confirmed by a similar switching behavior observed on ferromagnetically contacted carbon nanotube devices. The proposed model implies the realization of the transport via local Co chains embedded in the Alq{sub 3} layer and spin dependent tunneling over barriers at the interface Co grains/Alq{sub 3}/LSMO. The existence of conducting Co chains within the organics is supported by transmission electron microscopic/electron energy loss spectroscopic studies on cross-sectional samples from analogous layer stacks.

• OSTI ID: 21137245
• Journal Information: Journal of Applied Physics, Vol. 103, Issue 9; Other Information: DOI: 10.1063/1.2924435; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CARBON
COBALT
ELECTRIC POTENTIAL
ENERGY BEAM DEPOSITION
ENERGY LOSSES
ENERGY-LOSS SPECTROSCOPY
EVAPORATION
FERROMAGNETIC MATERIALS
LANTHANUM COMPOUNDS
LASER RADIATION
MAGNETORESISTANCE
NANOTUBES
ORGANIC SEMICONDUCTORS
PULSED IRRADIATION
SPUTTERING
STRONTIUM TITANATES
SUPERCONDUCTING JUNCTIONS
TEMPERATURE DEPENDENCE
TRANSMISSION ELECTRON MICROSCOPY
TUNNEL EFFECT