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Hamburg 2001 – scientific programme

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HL: Halbleiterphysik

HL 24: Poster II

HL 24.88: Poster

Thursday, March 29, 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 - Collaboration41Institut 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.

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