Berlin 2005 – scientific programme

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HL: Halbleiterphysik

HL 10: Spintronik II

HL 10.6: Talk

Friday, March 4, 2005, 16:15–16:30, TU P270

Very Large Tunneling Anisotropic Magnetoresistance in (Ga,Mn)As based tunnel structures. — •Christian Rüster¹, Charles Gould¹, Tomas Jungwirth², Jairo Sinova³, Gisela Schott¹, Karl Brunner¹, Georg Schmidt¹, and Laurens Molenkamp¹ — ¹Physikalisches Institut (EP3), Universität Würzburg, Würzburg, Germany — ²Institute of Physics ASCR, Praha 6, Czech Republic — ³Department of Physics, Texas A and M University, USA

We previously reported the discovery of tunneling anisotropic magnetoresistance, which manifests itself as spin-valve like behaviour in a normal-metal/insulator/ferromagnetic-semiconductor tunneling device, and results from a combination of the anisotropic density of states in the (Ga,Mn)As with respect to the magnetization direction, and a two-step magnetization reversal process in the material.

We now reports on the very large amplification of this effect in a fully epitaxial (Ga,Mn)As/GaAs/(Ga,Mn)As structure. In addition to raising questions about previous reports in the literature interpreting of spin valve behaviour in (Ga,Mn)As based structures as traditional tunneling magnetoresistance akin to that in metals, the effect reported here also exhibits several novel spintronics features: (i) Both normal and inverted spin-valve signals in a single device; (ii) a large non-hysteretic magnetoresistance for perpendicular magnetic fields; (iii) A sensitivity to the direction of the external magnetic field; (iv) Enormous amplification of the effect at low bias and temperatures to the point of behaving as a true on-off current switch.