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7 Acta Physica Polonica A

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On the Possible Analogy between Spin-Glasses and Systems

100%

Łusakowski A.

Acta Physica Polonica A

1992

tom 82

nr 4

620-622

An analogy between a spin-glass and a material containing DX centers is postulated. The basis of the analogy is the formal identity of the Hamiltonians of these two systems. A correspondence between parameters of the spin-glass and of the DX system is established. Experiments which could support the above idea are proposed.

Influence of Spin-Orbit Interaction on Band Structure and Elastic Properties of PbTe

63%

Radzyński T. , Łusakowski A.

Acta Physica Polonica A

2009

tom 116

nr 5

954-955

Inclusion of spin-orbit interaction in density functional theory calculations of PbTe band structure leads to wrong results concerning the symmetry of valence and conduction band wave functions. Using two ab initio codes: OpenMX and Quantum Espresso we show that changing the spin-orbit coupling strength in pseudopotentials for Pb it is possible to obtain proper energy gap and wave functions of proper symmetries.

Magnetic Anisotropy in GeMnTe - ab initio Calculations

63%

Łusakowski A. , Bogusławski P.

nr 5

1177-1179

Density functional theory calculations of the energy of magnetic anisotropy in GeMnTe were performed using OpenMX package with fully relativistic pseudopotentials. The discussion of microscopic origin of magnetic anisotropy was conducted. The main conclusion is that the magnetic anisotropy is caused by interplaty between spin-orbit and Coulomb interactions. The discussion includes also the influence of the free carriers concentration on the amplitude of energy of magnetic anisotropy. The important role of the chemical disorder is also pointed out.

On the Possible Origin of Large Value of Magnetic Anisotropy Constant in PbSnMnTe Mixed Crystals

51%

Łusakowski A. , Story T. , Gałązka R.

nr 4

829-831

In PbSnMnTe crystals with the concentration of conducting holes of the order of 10^{21} cm^{-3}, the magnetic anisotropy constant K measured in ferromagnetic resonance experiments is nearly one order of magnitude larger than expected. In the present paper we investigate a contribution ΔK to the anisotropy constant, origin of which is the s-d interaction and the spin-orbit coupling.

Magnetic Anisotropy in (Ge,Mn)Te Layers

51%

Knoff W. , Łusakowski A. , Wołoś A. , Story T.

nr 2

404-406

Ferromagnetic resonance study of magnetic anisotropy is presented for thin layers of IV-VI diluted magnetic semiconductor (Ge,Mn)Te with Mn content of 12 and 21 at.% grown by molecular beam epitaxy on BaF₂ (111) substrates. The layers with low Mn content grow in the rhombohedral crystal structure and exhibit perpendicular magnetic anisotropy whereas the layers with Mn content higher than about 20 at.% are of cubic (rock-salt) structure and show regular easy-plane type magnetic anisotropy. The quantitative analysis of the angular dependence of the ferromagnetic resonant field is performed taking into account the magnetic energy contributions due to rhombohedral distortion (axial term along the (111) growth direction of the layer) and the crystal field terms allowed for ferromagnetic systems of rhombohedral symmetry.

Raman Spectroscopy of Co-Doped ZnO Bulk Crystals

38%

Szuszkiewicz W. , Morhange J. , Gołacki Z. , Łusakowski A. , Schumm M. , Geurts J.

nr 2

363-368

Low-temperature Raman spectra of a bulk mixed crystal Zn_{1-x}Co_xO (x = 0.016) are shown and analyzed. Besides the common modes of the ZnO host lattice, electronic transitions related to the presence of Co^{2+} ions at the Zn sites are observed. In spite of the low Co concentration the presence of collective excitations corresponding to Co and CoO precipitates is also revealed.

Transport and Magnetic Study of Gd Ions in Pb_{1-y}Sn_{y}Te

32%

Story T. , Arciszewska M. , Łazarczyk P. , Łusakowski A. , Górska M. , Dobrowolski W. , Witkowska B. , Grodzicka E. , Gałązka R.

nr 5

997-1000

Electric conductivity, Hall effect and magnetic susceptibility of Pb_{1-x-y} Sn_{y}Gd_{x}Te 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 Pb_{1-y}Sn_{y}Te 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.