Regensburg 2004 – scientific programme

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HL: Halbleiterphysik

HL 35: Symposium Ferromagnetische Halbleiter

HL 35.6: Talk

Thursday, March 11, 2004, 12:45–13:15, H15

Modified magnetic properties of ordered arrays of (II,Mn)VI quantum wires due to reduced lateral dimensions — •P.J. Klar¹, L. Chen¹, W. Heimbrodt¹, F.J. Brieler², M. Fröba², T. Kurz³, H.-A. Krug von Nidda³, and A. Loidl³ — ¹Dept. Physics and Material Sciences Center, Philipps-University of Marburg, Germany — ²Institute of Inorganic and Analytical Chemistry, Justus-Liebig University of Gießen, Germany — ³Dept. Physics, University of Augsburg, Germany

We present a novel way of synthesising highly ordered arrays of (II,Mn)VI quantum wires with lateral dimensions of 3 nm to 9 nm and Mn-contents x between 0% and 100% by incorporating the semiconductor into mesoporous SiO₂ matrices. Quantum confinement increases the band gap by about 200 meV for Cd_1−xMn_xS and by about 150 meV for Zn_1−xMn_xS in the narrowest wires. A stronger p−d-hybridisation related band-gap bowing as a function of x occurs in the (Cd,Mn)S wires compared to bulk. The magnetic properties also change significantly. Compared to the bulk (II,Mn)VI compounds, a reduced antiferromagnetic coupling between the magnetic moments of the Mn²⁺ ions is found. For x ≥ 0.8, a full suppression of the paramagnetic to antiferromagnetic phase transition of the Mn-system is observed for the 3 nm wires. For 6 nm and 9 nm wires a phase transition occurs, but the Néel temperatures are smaller than in bulk. The observed behavior yields information about the length scale of the antiferromagnetic ordering. Similar effects are also anticipated for ferromagnetic wires.