Electron paramagnetic resonance (EPR) was investigated in samples of the magnetically diluted semiconductor Pbl "~Sn"Mn"Te in the temperature range T=1.3-100 K. The samples had compositions in the range x =0.005-0.06, y =0.12-0.72 and carrier concentrations between p =1.6X10' and 1.4X 10 ' cm . The temperature dependence of the EPR linewidth is strongly dependent on the carrier concentration. This can be understood within the framework of the Korringa relaxation mechanism and the two-valence-band model of magnetic properties of these crystals. For samples with high carrier concentrations (ferromagnetic at low temperatures) we obtained an s-d exchange integral of J,d = 33+2 meV.The role of metal vacancies in the effect of electron bottleneck of the EPR is also discussed.
Magnetization, susceptibility and specific-heat data for PbSn(Mn)Te and Sn(Mn)Te will be reported for various carrier concentrations, For the first time a carrier-concentration-induced breakdown of a ferromagnetic state has been observed. Based on a simple geometrical argument, a phase diagram for this new transition in RKKY-driven systems will be derived and will be compared with the ferromagnetic-to-spin-glass transition predicted by the well-known Sherrington-Kirkpatrick model.
The Ruderrnan-Kittel-Kasuya-Yosida (RKKY) indirect-exchange interaction via free carriers is analyzed in the case of IV-VI semimagnetic semiconductors (diluted magnetic semiconductors). Carriers responsible for the RKKY interaction in these materials originate from the anisotropic band of heavy holes located at the X point of the Brillouin zone (i.e. , there are 12 equivalent valleys of this band). Both intervalley and intravalley electron processes contribute to the exchange coupling. Calculations of the RKKY exchange integral and the paramagnetic Curie temperature (8) are presented. The exchange integral is anisotropic, and its dependence on the interspin distance is significantly modified in such a way that the role of antiferromagnetic couplings is increased. As a consequence, the value of 8 is reduced.
New measurements of the magnetic carrier-induced properties of Sn1−xMnxTe for x≤0.10 are presented. The results of these and previously reported measurements for other compositions and carrier concentrations will be compared to model calculations of the low-temperature magnetic state. A magnetic phase diagram will be presented.
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