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MSC Colloquium Laurens W. Molenkamp


06 January 2005 FWN-Building 5111.0080, Nijenborgh 4, 9747 AG, Groningen
Laurens W. Molenkamp
Laurens W. Molenkamp
Speaker: Dr. Laurens W. Molenkamp

Physikalisches Institut (EP3), Universität Würzburg,
Am Hubland, 97074 Würzburg, Germany

Title: Spintronic nanostructures
Date: Thu Jan 6, 2005
Start: 16.00 (Doors open and coffee available at 15.30)
Location: FWN-Building 5111.0080


Semiconductor spintronics has now reached a stage where the basic physical mechanisms controlling spin injection and detection are understood. Moreover, some critical technological issues involved in the growth and lithography of the magnetic semiconductors have been solved. This has allowed us to explore the physics of spintronic nanostructures.

As examples of such devices, I will discuss resonant tunneling diodes (RTDs) fabricated from paramagnetic II-VI semiconductors that can be operated as a voltage-controlled spin switch. A quantum-dot version of these RTDs exhibits, unexpectedly, remanent magnetism at zero external field, which we interpret as resulting from tunneling through a single magnetic polaron.

In the ferromagnetic semiconductor (Ga,Mn)As we have observed a very large spin valve effect due to domain wall pinning at sub-10 nm sized constrictions. Furthermore, we have found a novel magnetoresistance effect in this material, dubbed tunnel anisotropic magnetoresistance (TAMR), which is due to the strongly (magneto-)anisotropic density of states in a ferromagnetic semiconductor. The effect leads to the observation of a spin valve-like behavior in tunnel structures containg a single ferromagnetic layer and also dominates the spin-valve signal obtained from structures containing two (Ga,Mn)As layers, where the effect may cause resistance changes of five orders of magnitude.


Last modified:22 October 2012 2.30 p.m.