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1

Magnetite Fe_3O_4: the Correlated Electron-Phonon System

100%

Kozłowski A., Kąkol Z., Tarnawski Z.

Acta Physica Polonica A

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2007

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vol. 111

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issue 4

537-547

EN

In the paper the influence of magnetic as well as electron-lattice interactions on the Verwey transition in magnetite related compounds is discussed based on the authors' experimental activity and available literature. While magnetism was proved to only reflect the transition, the results of nuclear inelastic scattering show that lattice dynamics actively participates in it. The studies of diffuse neutron scattering and heat capacity suggest also that the low temperature lattice properties of slightly doped magnetite are distinct from those with higher dopant concentration. Finally, recent theoretical results strongly suggest that the Verwey transition in magnetite cannot be understood and described without strong involvement of electron-lattice interactions.

2

Professor Wojciech Włodarczyk at his 80

100%

Ziółko J., Giżejowski M., Kozłowski A.

Archives of Civil Engineering

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2010

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issue 3

3

Specific Heat and Magnetoresistance of Y-, Tl- and Bi-Type High-Temperature Superconductors

88%

Zalecki R., Kozłowski A., Kołodziejczyk A., Gritzner G., Mair M.

Acta Physica Polonica A

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1997

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vol. 91

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issue 2

431-434

EN

Specific heat of polycrystalline DyBa_{2}Cu_{3}O_{7} and Tl_{0.58}Pb _{0.42}Sr_{1.6}Ba_{0.4}Ca_{2}Cu_{3}O_{9} samples, as well as the single crystal of Bi_{2}Sr_{2}CaCu_{2}O_{8} have been measured within the temperature interval from 50 to 250 K. For Dy- and Tl-specimens the pronounced jump in specific heat and apparent contribution from Gaussian fluctuations of superconducting order parameter close to T_{c} have been observed. In contrary, for Bi-specimen only a rounded maximum within a broad interval around T_{c} has been detected. Magnetoresistance measurements as a function of temperature just below T_{c} have been carried out for Dy- and Tl-samples and the slopes of upper critical fields have been determined. The data have been analysed within a frame of Ginzburg-Landau-Abrikosov- Gorkov theory with additional Gaussian-like fluctuation term. The electronic specific heat coefficients γ, and the coherence length χ have been obtained.

4

Rhombohedral Distortion in Fe_{3-y}Zn_{y}O_{4} at Verwey Transition

88%

Kozłowski A., Kąkol Z., Zalecki R., Knight K., Honig J. M.

Acta Physica Polonica A

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1997

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vol. 91

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issue 2

443-446

EN

The time-of-flight neutron diffraction data were collected for two Fe_{3-y}Zn_{y}O_{4} powder samples showing different order of the Verwey transition: y=0.0072 - first order, y=0.0249 - second order. Measurements were performed on spallation neutron source in ISIS Rutherford Appleton Laboratory. At low temperatures (below Verwey transition temperature T_{V}) clear splitting of certain reflections characteristic of rhombohedral distortion was observed for both samples. We found that this distortion is much bigger for the sample exhibiting first-order than for the sample showing second-order transition.

5

Cation Distribution in Fe_{3(1-δ)}O_{4} and Low Level Doped Fe_{3-x}M_{x}O_{4}, M=Ti, Zn, Al

88%

Kąkol Z., Kozłowski A., Sabol J., Metcalf P., Honig J.

Acta Physica Polonica A

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1994

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vol. 85

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issue 1

223-227

EN

Systematic magnetic saturation moment and electrical resistivity measurements of the Fe_{3(1-δ)}O_{4} and Fe_{3-x}M_{x}O_{4} (M = Ti, Zn, Al) are presented. Cation distributions for low level doping are proposed and compositional dependencies of the Verwey transition temperature are determined. The latter show striking similarities in their dependence on cation vacancies and dopant concentration for any extraneous cations. These data are the basis for the analysis of the correlation between the presented cations distributions and the Verwey transition.

6

Electronic Band Structure and Photoemission States of Bi_{1.96}Mg_{0.04}Se_3

76%

Tokarz W., Zalecki R., Kowalik M., Kołodziejczyk A., Kozłowski A., Miotkowski J.

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vol. 126

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issue 4a

A-127-A-129

EN

We present theoretical band structure calculations and ultraviolet electron photoemission spectroscopy of a topological insulator Bi_{1.96}Mg_{0.04}Se_3. Our calculations were based on the first-principles density functional theory with general gradient approximation using Wien2k package with the spin-orbit interaction included by a second-variation method. The R3̅m crystal structure was optimized. In consequence, 4% decrease of volume and 3% decrease of ratio c/a was obtained. This modified structure was multiplied three times in a and b direction in order to place proper amount of Mg. Final crystal structure P3m1 with 135 atoms was used for the calculations. As a result metallic band structure was obtained with conduction band extended from -5.6 eV up to 0.16 eV. It composes mostly from Se p states. Comparison of total DOS with ultraviolet photoemission spectrum shows similar features.

7

Electronic Properties of High-Temperature Superconductor DyBa_{2}Cu_{3}O_{7} from Critical Fields and Specific Heat Studies

76%

Kołodziejczyk A., Kozłowski A., Chmist J., Zalecki R., Ściężor T., Tarnawski Z., Woch W.

Acta Physica Polonica A

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1993

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vol. 84

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issue 1

127-138

EN

The lower and upper critical fields, as well as the specific heat were measured as a function of temperature for good quality DyBa_{2}Cu_{3}O_{7} high-temperature superconductor in the vicinity of superconducting transition temperature T_{c} = 91.2 K. The number of superconducting and normal state electronic quantities were determined basing on the Ginzburg-Landau-Abrikosov-Gorkov theory. It is argued that on the basis of this BCS-like theory one can describe the superconducting properties and, in combination with some information on the electronic structure, also the magnetic properties of high-temperature superconductors.

8

Heat Capacity and Elastic Constants of Fe_{3-x}Zn_{x}O_{4} in the Vicinity of the Verwey Transition

76%

Kozłowski A., Kąkol Z., Schwenk H., Bareiter S., Hinkel C., Luthi B., Honig J.

Acta Physica Polonica A

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2000

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vol. 97

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issue 5

883-887

EN

The results of the heat capacity and elastic constant studies of Fe_{3-x}Zn_{x}O_{4} (x<0.04) series are reported. Adiabatic heat capacity measurements, performed on single crystals, show the clear change of the transition character from first order for low Zn content (x<0.012) to the higher order in 0.012

9

Studies of the Magnetic Axis Switching in Magnetite

76%

Król G., Kusz J., Tarnawski Z., Kąkol Z., Tabiś W., Kozłowski A.

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EN

The influence of the external magnetic field on magnetic and crystallographic structure of magnetite was studied. We have confirmed, by means of vibrating sample magnetometer measurements, that external magnetic field can switch the easy magnetic axis to the new crystallographic direction. We have also proved by the direct observation of the crystalline structure that this phenomenon is strictly related to the crystallographic structure relaxation.

Refine search results

Magnetite Fe_3O_4: the Correlated Electron-Phonon System

Professor Wojciech Włodarczyk at his 80

Specific Heat and Magnetoresistance of Y-, Tl- and Bi-Type High-Temperature Superconductors

Rhombohedral Distortion in Fe_{3-y}Zn_{y}O_{4} at Verwey Transition

Cation Distribution in Fe_{3(1-δ)}O_{4} and Low Level Doped Fe_{3-x}M_{x}O_{4}, M=Ti, Zn, Al

Electronic Band Structure and Photoemission States of Bi_{1.96}Mg_{0.04}Se_3

Electronic Properties of High-Temperature Superconductor DyBa_{2}Cu_{3}O_{7} from Critical Fields and Specific Heat Studies

Heat Capacity and Elastic Constants of Fe_{3-x}Zn_{x}O_{4} in the Vicinity of the Verwey Transition

Studies of the Magnetic Axis Switching in Magnetite