Berlin 2005 – scientific programme
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MA: Magnetismus
MA 15: Magnetische Kopplungsph
änomene / Exchange Bias
MA 15.7: Talk
Saturday, March 5, 2005, 15:30–15:45, TU H1028
Direct evidence for anti-ferromagnetically coupled Mn-Mn pairs in ZnGeP2 — •Wolfgang Gehlhoff1, Dmitri Azamat1, Axel Hoffmann1, and Valeriy Voevodin2 — 1Institute for Solid State Physics, Technical University Berlin — 2Siberian Physico-Technical Institute, Tomsk, Russian Federation
The ternary pnictides AIIMIVX2V have attracted much interest because of their nonlinear optical properties and the recent discovery of room temperature ferromagnetism in highly Mn-doped CdGeP2, ZnGeP2 and ZnSnAs2, which will enable new nonlinear magneto-optical device structures for nonlinear optics and spintronic applications. The origin of the ferromagnetism in these highly Mn-doped semiconductors is controversially discussed. To decide between the different predictions detailed knowledge concerning the incorporation of Mn in the different charge states on the different lattice site are necessary. For low Mn concentration in ZnGeP2 we found by electron paramagnetic resonance (EPR) studies a drastic Mn-induced change of the free parameter xf of the chalcopyrite structure, which can affect the formation of the stable magnetic state. For higher Mn concentration the formation of anti-ferromagnetically coupled MnZn2+-MnZn2+ pairs [1] could be confirmed by the finding of the characteristic hyperfine structures: 11 hyperfine lines with the characteristic intensity ratio 1:2:3:4:5:6:5:4:3:2:1 and a HF-splitting of 3.5mT, the half value of the HF-splitting of the isolated Mn2+ ion on Zn site.
W. Gehlhoff, D. Azamat, A. Hoffmann, Materials Science in Semiconductor Processing, Vol.6 (2003) pp. 379-383