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HL: Halbleiterphysik

HL 29: Spinabh
ängiger Transport I

HL 29.4: Vortrag

Mittwoch, 10. März 2004, 16:00–16:15, H13

Very large Magnetoresistance in ferromagnetic (Ga,Mn)As wires with Nanoconstrictions — •Christian Rüster, Tatjana Borzenko, Charles Gould, Georg Schmidt, and Laurens Molenkamp — Physikalisches Institut, Universität Würzburg, Am Hubland, D-97074 Würzburg

It was recently pointed out by Flatté and Vignale [APL 78, (2001) 1273] that a very large magnetoresistance should be observable from domain walls in (Ga,Mn)As. We have now fabricated, using e-beam lithography and dry etching, (Ga,Mn)As based nanostructures where domain walls can be pinned by sub-20 nm constrictions. Controlled by shape anisotropy we can switch the regions on either side of the constriction to either parallel or antiparallel magnetization. All samples exhibit a positive magnetoresistance when a domain wall is trapped at the constriction. We clearly observe the exponential I/V-characteristics predicted by Flatté and Vignale. For samples in the diffusive transport regime, we find a magnetoresistance up to 8%, while in samples where, due to depletion at the constriction, a tunnel barrier is formed, we observe magnetoresistance up to 2000%. Preliminary data on the manipulation of domain walls using electrical current is also presented.