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TT: Fachverband Tiefe Temperaturen

TT 37: Transport: Nanoelectronics II - Spintronics and Magnetotransport

TT 37.5: Vortrag

Donnerstag, 26. März 2009, 10:30–10:45, HSZ 105

Magnetic and transport properties of ferromagnet / semiconductor Heterostructures (Ga,Mn)As/GaAs — •S R Dunsiger¹, T Goko^2,3, J P Carlo², G Nieuwenhuys⁴, T Prokscha⁴, E Morenzoni⁴, D Chiba⁵, T Tanikawa⁵, F Matsukura⁵, H Ohno⁵, R H Heffner⁶, and Y J Uemura² — ¹Physik Dept E21, TU München, Garching, Germany — ²Dept of Physics, Columbia University, New York, USA — ³TRIUMF, Vancouver, Canada — ⁴PSI, Villigen, Switzerland — ⁵Laboratory for Nanoelectronics and Spintronics, RIEC, Tohoku University, Sendai, Japan — ⁶LANL, Los Alamos, USA

Ferromagnet-Semiconductor heterostructures show immense promise for device applications, in particular in the injection of polarised spins into a semiconducting substrate. More fundamentally, the III-V semiconducting materials (Ga,Mn)As exhibit unusual long range indirect exchange interactions between Mn ions, where the Mn atoms simultaneously act as a magnetic species and charge donors. An intriguing link between the magnetic and transport properties is hence implied.

Low-energy µ SR, in addition to magnetization and transport measurements on specimens with Mn concentrations between 1.0 and 3.4 % are reported. Ferromagnetism with a sharp onset temperature and nearly 100 % volume fraction is observed, at odds with debate over the rather inhomogeneous nature of the phase transitions. In addition, the semiconductor-to-metal transition and paramagnetic-to-ferromagnetic transitions occur at different Mn concentrations, while unusually, even a semiconducting film shows static ferromagnetism developing.