Electric conductivity, Hall effect and magnetic susceptibility of Ρb1-x-ySnyGdxTe mixed crystals with 0.13 < y < 0.93 and 0.001 < x < 0.04 were experimentally studied over the temperature range 4K < T < 300 K. The incorporation of Gd ions into the Pb1-ySnyΤe matrix results in semi-metallic n-type conductivity of the crystals with y < 0.6. For crystals with y > 0.6 one observes only semi-metallic p-type conductivity. We present a model explaining these results in terms of the Sn composition dependence of the location of Gd 2 +/3 + level with respect to the band edges of PbSnGdTe. In recent investigations of magnetic and transport properties of Sn 1 -x Gdx Te it was established that in SnTe Gd forms a resonant donor state with Gd 2 +/3+ energy level located about 0.2 eV below the top of the valence band [1]. Depending on the position of the Fermi level (governed by the concentration of two electrically active centers, Sn vacancies and Gd 3 + ions) with respect to the Gd 2 +/3+ energy level, we expect the Gd ions to be present in SnTe matrix both in the usual 3+ charge state (electron configuration 4f7) and in 2+ state (electron configuration 4f75d1 ).In SnTe Gd shows only limited donor action by partially compensating very high hole concentration due to native acceptor defects [1][2][3]. In related Pb 1 -x Gdx Te semiconducting crystals, Gd shows clear donor character generating the electron concentrations above n 10 20 cm-3 . In PbTe the Gd2+/3+ level is expected to be located far above the bottom of the conduction band. The purpose of our work is to examine the mixed Pb 1 -y Snν Τe crystals with Gd. It is expected that with an increasing content of Sn in Pb 1 -x -y Sn2 Gdx Τe, the Gd2+/3+ energy level will shift down from the conduction band to the valence band via the energy gap. It will result in a smooth change from the n-type to the p-type semi-metallic conductivity via a (possible) semi-insulating state. Similar effects were actually observed in PbSnTe with nonmagnetic In resonant donor [4].We studied a set of bulk Pb 1 -x -y Sny Gdx Τe crystals with y = 0.14, 0.30, 0.50, 0.67, 0.73 and 0.93, and with Gd content up to 4 at.%. We measured the Hall effect and the electric conductivity over the temperature range T = 4-300 K (997)
Hall constant, conductivity and magnetic susceptibility of Pb1-x-ySnyMnxTe semimagnetic semiconductor were investigated as a function of Mn content (x = 0.04, 0.09, 0.16, y = (0.7-0.8)) in the temperature range T = (4-300) K. A ferromagnetic phase transition takes place at T = 5 K for samples with x = 0.04, at T = 10 K for x = 0.09 and at T = 20 K for x = 0.16. For crystals with x > 0.09 the strong temperature dependence of the Hall constant is observed for temperatures below 40 K. Magnetic field characteristics of the Hall effect is strongly non-linear at T = 4.2 K. No significant temperature or magnetic field dependence of conductivity is observed in the whole temperature range studied. The observed transport anomalies are due to the anomalous Hall effect.
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