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1

The Magnetocaloric Effect in {[Cu(bapa)]₃[Cr(CN)₆]₂}ₙ · 6n H₂O at Low Temperatures

100%

Ráczová K., Vavra M., Hegedüs M., Čižmár E.

Acta Physica Polonica A

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2018

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vol. 133

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issue 3

429-431

EN

The crystals of {[Cu(bapa)]₃[Cr(CN)₆]₂}ₙ·6nH₂O (bapa = bis(3-aminopropyl)amine) are formed by infinite Cu(II)-Cr(III) antiparallel chains, which are connected into the third direction by additive [Cu(bapa)] moieties. The onset of long-range magnetic order at 3.2 K was observed by AC susceptibility. The study of the magnetocaloric effect from magnetization measurements yields a large entropy change -ΔS_{M} = 13.65 J K¯¹mol¯¹ (-ΔS_{M} = 12.25 J kg¯¹K¯¹) at the field change from 0 T to 3 T at temperature 4 K. The analysis of the critical behavior of -ΔS_{M} suggests the value of critical exponent n = 0.577 at the ordering temperature characteristic for three-dimensional magnets with Ising anisotropy.

2

Magnetism in NdMnO_{3+δ} Studied by the Single Crystal Neutron Diffraction

100%

Mihalik M., Mihalik M., Maťaš S., Vavra M.

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vol. 126

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issue 1

284-285

EN

We present the single crystal neutron diffraction experiment performed on the NdMnO_{3+δ} compound. The aim of the experiment was to study/revisit the magnetic structure of the compound. We have confirmed the ordering of Mn sublattice below T_{N}=85.5 K and confirmed that the Nd sublattice orders below T_{1} ≈ 20 K with Nd moments aligned parallel to the b-axis.

3

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.

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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.

4

Magnetic Properties of (Cu_{x}Mn_{1-x})_3[Cr(CN)_6]_2·zH_2O Complexes

76%

Vavra M., Antoňák M., Jagličić Z., Mihalik M., Mihalik M., Csach K., Zentková M.

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issue 5

998-999

EN

Magnetization measurements were performed on the (Cu_{x}Mn_{1-x})_3[Cr(CN)_6]_2·zH_2O molecule-based magnets where x=0.0, 0.2, 0.25, 0.3, 0.35 0.4, 0.6, 0.8 and 1.0. Both the Curie temperature and saturated magnetization at first decrease with increasing value of x reaching the minimal value of T_{C} = 49.7 K and 0.17 μ_{B} for x=0.2 and then increase with substitution. The pronounced hysteretic behavior between zero-field cooled and field cooled regimes was observed for all samples. Magnetization changes the sign of magnetic polarization in zero-field cooled magnetization curve at the compensation temperature T_{comp} = 16 K for sample with x = 0.4. Our results indicate that the system behaves as mixed-ferri-ferromagnetic system.

5

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.

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vol. 126

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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.

6

Magnetic Properties of La_{0.85}Ag_{0.15}MnO_{3} Nano-Powders Under Pressure

64%

Antoňák M., Mihalik M., Zentková M., Mihalik M., Vavra M., Lazúrová J., Fitta M., Balanda M.

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vol. 126

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issue 1

296-297

EN

In our paper we present effect of pressure on magnetic properties of La_{0.85}Ag_{0.15}MnO_{3} nanopowders prepared by glycine-nitrate method. The particle size and crystal structure were modified by heat treatment. The average size of particle varies from about 25 nm for as prepared sample to 60 nm for annealed sample. Crystal structure changes from orthorhombic to rhombohedral after annealing at 600 °C/2 hours. The Curie temperature increases with annealing and is more than doubled after annealing at 600 °C/2 hours. The exchange bias phenomenon was observed in samples with orthorhombic crystal structure with average particle size of about 25 nm. Pressure effect on the Curie temperature T_{C}, saturated magnetization μ_{s} and exchange bias field H_{E} is negligible in this case. In the case of the samples with rhombohedral structure, T_{C}, μ_{s} and remnant magnetization μ_{r} increase with pressure; the coercive field decreases with pressure.

7

Exchange Bias Effect in NdFeO₃ System of Nanoparticles

64%

Vavra M., Zentková M., Mihalik M., Mihalik Jr. M., Lazúrová J., Girman V., Perovic M., Kusigerski V., Roupcova P., Jaglicic Z.

Acta Physica Polonica A

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2017

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vol. 131

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issue 4

869-871

EN

We study the effect of nanometric size on the crystal structure, magnetic environment of iron and magnetization in NdFeO₃ system of nanoparticles. The average particle size of NdFeO₃ nanoparticles increases with annealing at 600°C from about 15 nm to 40 nm. The smallest particles on annealed sample have size approximately 30 nm and typically have character of single crystalline samples. All samples adopt orthorhombic crystal structure, space group Pnma with lattice parameters a =5.5817 Å, b=7.7663 Å and c =5.456 Å for as prepared sample. The presence of superparamagnetic particles was indicated by the Mössbauer measurements. The reduction of dimensionality induces a decrease of T_{N1} from 691 K to 544 K. The shift of magnetic hysteresis loop in vertical and horizontal direction was observed at low temperatures after cooling in magnetic field. We attribute such behaviour to exchange bias effect and discuss in the frame of core-shell model.

8

Effect of the Jahn-Teller Distortion on Double Exchange Interaction in La_{0.8}K_{0.2}MnO₃ Nanoparticles

64%

Mihalik M., Zentková M., Vavra M., Mihalik Jr. M., Lazúrová J., Girman V., Konieczny P., Fitta M., Il'kovič S.

Acta Physica Polonica A

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2017

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vol. 131

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issue 4

875-877

EN

Electric resistance and effect of hydrostatic pressure on magnetic properties has been studied on the La_{0.8}K_{0.2}MnO₃ nanoparticles. Magnetic phase transition is affected by pressure only slightly, the Curie temperature T_{C} decreases with the rate of -1.02 K/GPa, on samples with orthorhombic structure where the Jahn-Teller distortion of lattice is large. On the other hand, T_{C} increases with the rate of 20.1 K/GPa on samples with rhombohedral structure, where the Jahn-Teller distortion of lattice is absent. Insulator type of electrical resistance is characteristic feature of sample with large Jahn-Teller distortion of lattice and insulator-metal transition was observed on samples where the Jahn-Teller distortion is negligible. Our results are in line with theoretical calculation predicting that double exchange interaction is suppressed by the Jahn-Teller distortion.

Refine search results

The Magnetocaloric Effect in {[Cu(bapa)]₃[Cr(CN)₆]₂}ₙ · 6n H₂O at Low Temperatures

Magnetism in NdMnO_{3+δ} Studied by the Single Crystal Neutron Diffraction

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

Magnetic Properties of (Cu_{x}Mn_{1-x})_3[Cr(CN)_6]_2·zH_2O Complexes

Magnetostructural Correlations of Nano-Sized Manganites Prepared by Different Ways

Magnetic Properties of La_{0.85}Ag_{0.15}MnO_{3} Nano-Powders Under Pressure

Exchange Bias Effect in NdFeO₃ System of Nanoparticles

Effect of the Jahn-Teller Distortion on Double Exchange Interaction in La_{0.8}K_{0.2}MnO₃ Nanoparticles