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1

Magnetic Specific Heat Study of the Competition between Ferro- and Antiferromagnetic Spin-Spin exchange Interactions in PbSnMnTe

100%

Łazarczyk P., Jędrzejczak A., Story T., Arciszewska M., Gałązka R.

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EN

Magnetic contribution to the specific heat, magnetic susceptibility and Hall effect are experimentally studied in Pb_{1-x-y}Sn_{y}Mn_{x}Te semimagnetic semiconductors with y=0.72 and x=0.08 and with different carrier concentrations 10^{20} ≤ p ≤ 10^{21} cm^{-3}. The ferromagnetism observed in crystals with p ≥ 3×10^{20} cm^{-3} breaks down with a decreasing concentration of carriers due to an increasing competition between Ruderman-Kittel-Kasuya-Yoshida and superexchange interactions.

2

Magnetic Specific Heat of Pb_{1-x}Eu_xTe

86%

Górska M., Łusakowski A., Jędrzejczak A., Gołacki Z., Anderson J., Balci H.

Acta Physica Polonica A

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2004

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vol. 105

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issue 6

631-636

EN

The temperature dependence of the magnetic specific heat was studied experimentally and theoretically in the semimagnetic semiconductor Pb_{1-x}Eu_xTe for x=0.027 and x=0.073, over the temperature range from 0.5 K to 15 K, in magnetic fields up to 2 T. In zero magnetic field at about 2 K there was a broad maximum in the magnetic specific heat, which was much higher than that predicted by the model of superexchange interaction between nearest neighbors; the maximum values increased with magnetic field. The experimental data were analyzed in the framework of a model which takes into account the spin splitting of the ground state of a single Eu2+ ion in the presence of local lattice distortions in the Pb_{1-x}Eu_xTe mixed crystal. The model describes well the experimental data, especially for lower x-values, where the contribution from singlets dominates.

3

Pb_{1-x}Mn_xTe Crystals as a New Thermoelectric Material

86%

Osinniy V., Jędrzejczak A., Domuchowski W., Dybko K., Witkowska B., Story T.

Acta Physica Polonica A

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2005

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vol. 108

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issue 5

809-816

EN

We studied experimentally thermoelectric properties of p-type bulk crystals of Pb_{1-x}Mn_xTe and Pb_{1-x-y}Ag_yMn_xTe (0≤ x≤ 0.083 and y≤0.017) at room and liquid nitrogen temperatures. Model calculations of the thermoelectric figure of merit parameter (Z) involved the analysis of carrier concentration, carrier mobility, density of states as well as electronic and lattice contributions to the thermal conductivity of PbMnTe. In the analysis we took into account the main effect of Mn concentration on the band structure parameters of PbMnTe, i.e. the increase of the energy gap. The analysis of electrical, thermoelectric, and thermal properties of Pb_{1-x}Mn_xTe crystals showed that, at room temperature, the maximum values of the parameter Z occur in crystals with Mn content 0.05≤ x≤0.07 and are comparable with a maximal value of Z observed in PbTe. At T=400 K the increase in the parameter Z by 10% is expected in Pb_{1-x}Mn_xTe crystal (as compared to PbTe) for a very high concentration of holes of about p=5×10^{19} cm^{-3}. The experimental data correctly reproduce the theoretical Z(p) dependence.

4

Fermi Level Position in GaMnAs - a Thermoelectric Study

86%

Osinniy V., Jędrzejczak A., Arciszewska M., Dobrowolski W., Story T., Sadowski J.

Acta Physica Polonica A

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2001

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vol. 100

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issue 3

327-334

EN

Thermoelectric power was studied in the temperature range 100≤ T≤300 K in 0.3-1μm thick ferromagnetic Ga_{1-x}Mn_xAs epitaxial layers (0.015≤ x≤0.06) in order to determine Fermi energy E_F and carrier concentration p. For 0.015≤ x≤0.05, at T=273 K we find E_F=275±50 meV and p=(2.5± 0.5)×10^{20} cm^{-3} (approximately Mn content independent). For x= 0.06, the Fermi energy decreases by about 100 meV with the corresponding reduction of hole concentration to p=1.2×10^{20} cm^{-3}. At T=120 K, these parameters vary between E_F=380 meV and p=3.5×10^{20} cm^{-3} for x=0.015 to E_F=110 meV and p=5×10^{19} cm^{-3} for x=0.06.

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4 Acta Physica Polonica A

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4 Jędrzejczak A.

3 Story T.

2 Arciszewska M.

2 Osinniy V.

1 Anderson J.

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1 Dobrowolski W.

1 Domuchowski W.

1 Dybko K.

1 Gałązka R.

1 Gołacki Z.

1 Górska M.

1 Sadowski J.

1 Witkowska B.

1 Łazarczyk P.

1 Łusakowski A.

Magnetic Specific Heat Study of the Competition between Ferro- and Antiferromagnetic Spin-Spin exchange Interactions in PbSnMnTe

Magnetic Specific Heat of Pb_{1-x}Eu_xTe

Pb_{1-x}Mn_xTe Crystals as a New Thermoelectric Material

Fermi Level Position in GaMnAs - a Thermoelectric Study