Search results

1

Spin Polarons in Two-Dimensional Systems

100%

Morkowski J.

Acta Physica Polonica A

|

2000

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vol. 97

|

issue 1

101-110

EN

The problem of motion of holes on a square lattice of antiferromagnetically ordered spins is considered. An overview of the theory of hole dynamics in the antiferromagnetic background is presented. Motion of a single hole is rather well understood both by numerical and analytical methods. For small but finite concentration of holes a treatment analogous to the standard polaron theory is discussed starting with an exact mapping of the t-J Hamiltonian into holon and pseudospin variables.

2

Spin Polarons in Antiferromagnetic Planes

100%

Morkowski J.

Acta Physica Polonica A

|

2007

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vol. 111

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issue 4

397-408

EN

In the lecture the theory of spin polarons is reviewed on the basis of its analogy with the theory of lattice polarons. The energy dispersion curve for a single polaron in a two-dimensional antiferromagnetic square lattice is calculated in the self-consistent Born approximation. Also in self-consistent Born approximation the energy of a pair of interacting spin polarons is calculated. The results of calculations for realistic values of parameters of the model lead to the conclusion that pairing of spin polarons is not a likely mechanism of superconductivity in cuprates.

3

Ab initio Calculations of the Magnetocrystalline Anisotropy in UAuSb_2 Ferromagnet

63%

Morkowski J., Szajek A.

Acta Physica Polonica A

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2009

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vol. 115

|

issue 1

185-187

EN

The paper presents results of ab initio calculations of the magnetocrystalline anisotropy of UAuSb_2, a strongly anisotropic ferromagnet below 36 K. The total energy of the unit cell of UAuSb_2 was calculated by two methods: the full potential linear muffin-tin orbitals method and by the full-potential local-orbital minimum basis band structure code. The computations were done for the following quantization directions in the tetragonal unit cell (orientations of the magnetization vector M): [010], [001], [011], [110], [111], and [11½] . The anisotropic contribution to the total energy for various directions were fitted by the least-squares procedure to the expression for the magnetocrystalline energy suitable for tetragonal symmetry E_A=K(α_x^4 +α_y^4)+ K_2α_z^2, where (α_x,α_y,α_z) is a unit vector along the direction of magnetization M. The band structure calculations predict the direction [111] as the easy axis of magnetization. Values of the calculated anisotropy constants at T=0 are provided.

4

Electronic Band Structure and Calculated Photoemission Spectra of USi_{3} Compound

51%

Morkowski J., Szajek A., Jezierski A.

Acta Physica Polonica A

|

1997

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vol. 92

|

issue 2

303-306

EN

The electronic band structure for USi_{3} was recalculated for varying ratios of the Wigner-Seitz radii, for U and Si atoms. The partial densities of states were used to calculate photoemission spectra which were compared with available experimental data.

5

Electronic Structure and X-Ray Photoemission Spectra of MPtSn ( rm M = Ti, Zr, Hf)

45%

Morkowski J., Szajek A., Chełkowska G., Bajorek A., Troć R.

Acta Physica Polonica A

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2009

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vol. 115

|

issue 5

935-940

EN

The electronic structures of the half-Heusler isostructural compounds TiPtSn, ZrPtSn and HfPtSn were calculated and measured applying the X-ray photoemission spectroscopy. The (Ti, Zr, Hf)PtSn compounds have gaps between the occupied valence band and the empty conduction band, calculated as about 0.75, 1.12, and 1.09 eV, respectively. The calculations were done by the full-potential local orbitals method in the framework of the local spin-density approximation and partly also by the full-potential linear muffin-tin orbitals method by the LmtART code. Experimental X-ray photoemission spectra were measured using photons of energy of 1486.6 eV. The experimental and calculated spectra match quite well except a small shift in the energy scale.

6

Proceedings of the European Conference Physics of Magnetism 96. Preface.

39%

Krompiewski S., Micnas R., Fechner B., Kowalewski L., Morkowski J., Szajek A., Thomas M.

Acta Physica Polonica A

|

1997

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vol. 91

|

issue 1

3-6

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Spin Polarons in Two-Dimensional Systems

Spin Polarons in Antiferromagnetic Planes

Ab initio Calculations of the Magnetocrystalline Anisotropy in UAuSb_2 Ferromagnet

Electronic Band Structure and Calculated Photoemission Spectra of USi_{3} Compound

Electronic Structure and X-Ray Photoemission Spectra of MPtSn ( rm M = Ti, Zr, Hf)

Proceedings of the European Conference Physics of Magnetism 96. Preface.