Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 20: Focus Session: Magnetic Semiconductors (jointly with MA)
HL 20.7: Vortrag
Montag, 26. März 2012, 18:00–18:15, EW 202
Magnetotransport in (Ga,Mn)As/GaAs core-shell nanowires — •Christian Butschkow1, Elisabeth Reiger1, Stefan Geißler1, Alexander Eckrot1, Andreas Rudolph1, Marcello Soda1, Dieter Schuh1, Georg Woltersdorf1, Werner Wegscheider2, and Dieter Weiss1 — 1Universität Regensburg, Germany — 2ETH Zürich, Switzerland
We investigate angle dependent the transport properties of individual ferromagnetic (Ga,Mn)As/GaAs core-shell nanowires in a magnetic field at cryogenic temperatures. The nanowires are grown self-assembled in a bottom up process using the vapor-liquid-solid (VLS) mechanism and molecular beam epitaxy (MBE). We observe a very pronounced response of the magnetoresistance on an applied magnetic field, which we attribute to the negative magnetoresistance effect (NMR) in combination with an effective magnetic field. This effective magnetic field, which is typically used to describe ferromagnetic resonance phenomena, is composed of the anisotropy field Ha and the external magnetic field. The shape of the resulting MR-traces can be used to derive the magnetic properties of single nanowires. This way we determine a Curie-Temperature of TC ≈ 20K and a strong uniaxial magnetic anisotropy with a magnetic easy axis pointing along the nanowire axis. We assume that this uniaxial magnetic anisotropy is related to strain relaxation similar to the observations on lithographically defined (Ga,Mn)As stripes. However we determine a uniaxial anisotropy constant KU which is up to 5 times larger than KU of the etched (Ga,Mn)As stripes.