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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

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.

3

Inter- and Intragrain Magnetization of Thallium-Based Superconductors

88%

Tokarz W., Kąkol Z., Kołodziejczyk A., König W., Gritzner G.

Acta Physica Polonica A

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2000

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vol. 98

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issue 5

633-636

EN

We report on magnetization and magnetic hysteresis measurements for the (Tl_{0.6}Bi_{0.5})(Sr_{0.9}Ba_{0.1})_{2}Ca_{2}Cu_{3}O_{y} Ag-sheathed superconducting tape as well as for the powdered and bulk (Tl_{0.6}Pb_{0.5})(Sr_{0.9}Ba_{0.1})_{2}Ca_{2}Cu_{3}O_{y} superconductors. For the investigated tape and bulk specimens the low field magnetization showed a deviation from the ideal linear M(H) dependence, which was attributed to the superposition of inter- and intragrain superconducting currents. Fitting of the theoretical magnetization curves to the experimental data allowed for the independent determination of the intragrain critical current densities for the superconducting grains and intergrain critical current densities for the weak link system at 77K.

4

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.

5

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

6

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.

7

Studies of the Verwey Transition in Magnetite

64%

Tarnawski Z., Wiecheć A., Madej M., Nowak D., Owoc D., Król G., Kąkol Z., Kolwicz-Chodak L., KozŁowski A., Dawid T.

Acta Physica Polonica A

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2004

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vol. 106

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issue 5

771-775

EN

Studies of the specific heat and simultaneous AC magnetic susceptibility (ρ') and electric resistance of stoichiometric magnetite single crystal are presented. The temperature hysteresis of the Verwey transition is of 0.03 K found from the specific heat data confirming its first-order character. The continuous temporal change of ρ' at T_V can be switched off by an external magnetic field without affecting the transition. The electrical resistance decreases continuously with increasing temperature with a rapid change of slope at the point when the phase transition is completed. It was concluded that the magnetic degrees of freedom do not actively participate in the transition and that the entropy released at T_V may come from ordering electrons.

Refine search results

Magnetite Fe_3O_4: the Correlated Electron-Phonon System

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

Inter- and Intragrain Magnetization of Thallium-Based Superconductors

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

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

Studies of the Verwey Transition in Magnetite