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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 A^IIM^IVX₂^V 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 x_f of the chalcopyrite structure, which can affect the formation of the stable magnetic state. For higher Mn concentration the formation of anti-ferromagnetically coupled Mn_Zn²⁺-Mn_Zn²⁺ 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