Berlin 2005 – scientific programme

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HL: Halbleiterphysik

HL 29: Spintronik IV

HL 29.1: Talk

Saturday, March 5, 2005, 15:00–15:15, TU P270

Preferred sites and valence states of transition metals in spintronic ZnGeP₂ — •Wolfgang Gehlhoff¹, Dmitri Azamat¹, Axel Hoffmann¹, and Nikolaus Dietz² — ¹Institute for Solid State Physics, Technical University Berlin, Germany — ²Department of Physics and Astronomy, Georgia State University, Atlanta, USA

The quest for room-temperature ferromagnetic semiconductors resulted in a recent interest in transition metal (TM) doped ternary pnictides A^IIM^IVX₂^V. The site preference and valence states for the different TM and their interaction with native defects play an important role in the discussion of the origin of the ferromagnetism [1, 2]. However, there are only few experimental data for the ternary pnictides [3]. For low Mn-doped samples the characteristic Mn²⁺ EPR spectra for isolated Mn²⁺ on group II site are observed. In higher doped ZnGeP₂ we observed the formation of Mn-Mn pairs. In addition, we could detect new TM defects in unintentionally doped ZnGeP₂.Without illumination of the samples we observed two iron-related spectra. The first one is identified as the spectrum of Fe²⁺ (3d⁶) incorporated on the Zn site with S=2 and a large zero-field splitting. The second one arises from Fe³⁺ (3d⁵) with S=5/2 and substitute for Ge site. Under illumination we observed the spectrum from Fe⁺ on Zn site. The strongest Cr-related spectrum is caused by Cr⁴⁺ on Ge site.
P. Mahadevan and A. Zunger, Phys. Rev. Lett. 88, 047205 (2002)
T. Kamatani and H. Akai, Phase Transitions 76, 401 (2003)
W. Gehlhoff, D. Azamat, A. Hoffmann, Materials Science in Semiconductor Processing, Vol.6 (2003) pp. 379-383