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1

Mechanosynthesis and Sintering of Ce_{1-x}Y_xO_{2-δ} (x ≤ 0.35) Solid Solutions

100%

Fabián M., Briančin J., Schutz T.

Acta Physica Polonica A

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2014

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vol. 126

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issue 4

951-953

EN

One-step mechanochemical approach was used to synthesize nanocrystalline Ce_{1-x}Y_xO_{2-δ} (x ≤ 0.35) solid solutions. X-ray powder diffraction was utilized to characterize crystalline phases of as-prepared products. It was shown that the presence of yttrium suppresses the crystal growth. The effect of yttrium content on the grain size before and after sintering of green bodies at high temperatures was evaluated by means of scanning electron microscopy. The combination of one-step mechanochemical process and relatively low sintering temperatures resulted in preparation of ceria-based ceramics with wide scale of possible applications.

2

Magnetic Properties of La_{0.8}K_{0.2}MnO_{3} Nanoparticles

76%

Mihalik M., Zentková M., Briančin J., Fitta M., Mihalik M., Lazúrová J., Vavra M.

Acta Physica Polonica A

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2014

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vol. 126

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issue 1

312-313

EN

Magnetic properties of La_{0.8}K_{0.2}MnO_{3} have been studied on nanoparticles prepared by glycine-nitrate method. Crystal structure and particles size were modified by heat treatment. Crystal structure changes from orthorhombic (space group Pbma) to rhombohedral (space group R-3c) after annealing at 600°C/2 hours. The average size of particle varies with annealing from about 30 nm to 135 nm. The Curie temperature T_{C} and the saturated magnetization μ_{s} increase with annealing. The exchange bias effect was observed on samples with particles size smaller than 60 nm.

3

Hall Effect in ZnO Extrinsic Structure

64%

Dolník B., Kurimský J., Marton K., Kolcun M., Tomčo L., Briančin J., Fabián M., Halama M., Vojtko M., Rajňák M.

Acta Physica Polonica A

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2014

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vol. 126

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issue 1

76-77

EN

Zinc oxide-based extrinsic composite was investigated. The sample was selected from a series of components of one production batch, prepared by standard sintering technology. The content of extrinsic elements in ZnO base was determined by SEM. Van der Pauw method with four-point electrode fixture was used for study of conducting phenomena in square-shaped sample. It is normaly preferred to assume the symmetric uniformity of the electrical properties of sample, for which sheet resistance, bulk resistivity and Hall mobility, sheet carrier density and carrier concentration can be calculated. When the uniformity of measured parameters is breached, the anisotropy in the arrangement of the internal structure may be the cause. There remains the question of whether the extrinsic ZnO material can be isotropic, regarding the electrical conductivity. Although the Hall effect has been measured, preliminary measurements indicate the presence of anisotropy in the measured samples. Before measurement the following phenomena should be taken into account: magneto-electric effect, photo-electric effect and the isothermal condition should be preserved. Paper discusses the uniformity deviations for the defined setup configurations for positive and negative magnetic field directions. Bulk resistivity has been calculated by numerical solution of van der Pauw equation. Large offset voltage during the measurement is discussed.

4

Magnetostructural Correlations of Nano-Sized Manganites Prepared by Different Ways

64%

Vavra M., Mihalik M., Mihalik M., Zentková M., Lazurová J., Matik M., Briančin J., Arnold Z., Maryško M.

Acta Physica Polonica A

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2014

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vol. 126

|

issue 1

304-305

EN

We present the preparation and magnetostructural correlations of binary NdMnO_{3} oxide prepared by four different procedures. Nano-size particle were prepared by simple precipitation of hydroxides (PH), nitrate-glycine synthesis (NG) and self-combustion high-temperature synthesis (SHS), while sol-gel method (SG) produced particles with size of about 2 μm. The as prepared PH and SG particles exhibit amorphous structure, the orthorhombic crystal structure was observed for NG and SHS particles. As prepared PH, NG and SHS are magnetically ordered, annealing leads to magnetic ordering of SG particles.

5

Magnetic Properties of NdFe_{0.9}Mn_{0.1}O_{3}

64%

Zentková M., Lazúrová J., Kováč J., Mihalik M., Mihalik M., Briančin J., Fitta M., Kusigerski V.

Acta Physica Polonica A

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2014

|

vol. 126

|

issue 1

306-307

EN

In our paper we study effect of Mn for Fe substitution on magnetic properties of NdFe_{x-1}Mn_{x}O_{3} compounds for x=0 and 0.1, which have been grown by the OFZ technique. The Néel temperature decreases from T_{N1}=691 K to T_{N1}=621 K, and the anomaly in AC susceptibility, related to spin reorientation, vanishes with Mn substitution. Low temperature heat capacity measurement for sample with x=0.1 revealed that substitution of Mn for Fe shifts a Schottky-type anomaly at T_{sh} to higher temperatures. Another anomaly is generated by doping at T_{max}=11 K. The anomaly is smeared out by magnetic field, confirming its magnetic origin.

6

The Response of a Magnetic Fluid to Radio Frequency Electromagnetic Field

52%

Dolník B., Rajňák M., Cimbala R., Kolcunová I., Kurimský J., Balogh J., Džmura J., Petráš J., Kopčanský P., Timko M., Briančin J., Fabián M.

Acta Physica Polonica A

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2017

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vol. 131

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issue 4

946-948

EN

Electromagnetic pollution generated by the electrical devices has been regarded as a new form of pollution, harmful to the society as air and water pollution. The operation of electronic devices in a polluted electromagnetic environment has caused electromagnetic interference to become important concerns. Devices that are vulnerable to interference must often be shielded to protect them from the effects of electromagnetic interference. In this work we describe an interaction of a magnetic fluid based on transformer oil with alternating magnetic field. The magnetic fluid was composed of a transformer oil and dispersed magnetite nanoparticles coated with oleic acid. Among the wide range of topics covered, we pay attention to an important field related to the absorption of electromagnetic field by magnetic fluid as a suitable candidate for applications where it is necessary to electrically isolate, remove excess of heat, and to shield electromagnetic fields. We present a method for the determination of shielding effectiveness of the magnetic fluid under high-frequency excitation conditions from 750 MHz to 3 GHz by means of magnetic near field measurements and analysis. Herein, we report the effect of magnetic volume fraction in the magnetic fluid and the effect of the sample thickness on the shielding effectiveness. We have found that the magnetic fluid has a frequency dependent "windows", characterized that either absorb the magnetic field, or facilitate penetration of the magnetic field through the barrier.

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1 Arnold Z.

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1 Kováč J.

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1 Maryško M.

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1 Schutz T.

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Mechanosynthesis and Sintering of Ce_{1-x}Y_xO_{2-δ} (x ≤ 0.35) Solid Solutions

Magnetic Properties of La_{0.8}K_{0.2}MnO_{3} Nanoparticles

Hall Effect in ZnO Extrinsic Structure

Magnetostructural Correlations of Nano-Sized Manganites Prepared by Different Ways

Magnetic Properties of NdFe_{0.9}Mn_{0.1}O_{3}

The Response of a Magnetic Fluid to Radio Frequency Electromagnetic Field