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HL: Halbleiterphysik

HL 24: Poster II

HL 24.88: Poster

Donnerstag, 29. März 2001, 10:30–19:00, Rang S\ 3

Behaviour of doping atoms in ferromagnetic semiconductors as investigated by hyperfine interactions — •V. Samokhvalov ¹, I. Burlakov ¹, G. Erfurt ¹, S. Unterricker ¹, M. Dietrich², I. Tiginyanu³, and ISOLDE - Collaboration⁴ — ¹Institut für Angewandte Physik, TU Bergakademie Freiberg, D-09596 Freiberg/Sachsen — ²Fachbereich Physik, Universität Konstanz, D-78457 Konstanz — ³Technical University of Moldova, 2004 Chisinau, Moldova — ⁴CERN-Geneva, Switzerland

HgCr₂Se₄ and CdCr₂S₄ are spinel-type ferromagnetic semiconductors with a Curie temperature of 106 K and 84 K, respectively. By aimed doping of proper elements one can vary their properties in a wide range. That is why the exact position as well as the behavior of doping atoms after different thermal treatments is important. The perturbed angular correlation method (PAC) allows us to determine site occupations of probes on an atomic scale. The hyperfine fields, namely, electric field gradients and magnetic hyperfine fields were measured by means of the radioactive PAC-probes ^111mCd, ¹¹¹Ag(¹¹¹Cd), ¹¹¹In(¹¹¹Cd), ¹¹⁷Cd(¹¹⁷In), ⁷⁷Br(⁷⁷Se), and ^199mHg implanted at ISOLDE on-line separator at CERN/Geneva. All probes except ¹¹¹In(¹¹¹Cd) unambiguously occupy certain lattice sites regardless of a thermal treatment. Only in the case of In-probes A- and B-site occupation is possible depending on the substances and thermal treatments. It amounts to 30-50% and 60-75% of A-site substitution for CdCr₂S₄ and HgCr₂Se₄, respectively. Measured hyperfine fields were compared with those calculated by the WIEN97-code.