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1
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Magnetic and Transport Properties of PrNi Single Crystal

100%
Maťaš S., Zentková M., Mihalik M.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
319-322
EN
Frequency dependence of χ"(T), different position of a maximum in χ"(T) for different crystal orientations, hysteretic behavior between magnetization measurements in zero-field cooling and field coolding regime are attributed to strong magneto-crystalline anisotropy of PrNi ferromagnetic single crystal with T_C=20.5 K, which is driven by crystal field effect. Applied pressure shifts T_C to higher temperatures (dT_C/dp=1 K/GPa). Susceptibility follows the Curie-Weiss law except for b-axis, which is hard magnetic axis. An anisotropic behavior was seen in resistivity measurements with the largest difference between b-axis and c-axis. Resistivity below T_C can be described by power law with ρT^{2.24} and is field dependent with a positive magnetoresistance.
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Magnetic Properties of Thorium Ferricyanide

88%
Göbl R., Zentková M., Kavečanský V., Kováč J., Zentko A.
Acta Physica Polonica A
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2000
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vol. 97
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issue 5
835-838
EN
The magnetic properties of Th_{3}[Fe(CN)_{6}]·10H_{2}O were investigated. It was shown that this compound is antiferromagnetically ordered in the low temperature region. The observed antiferromagnetic ordering is stable only in the low field.
3
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Magnetic and Transport Properties of La_{0.67}Pb_{0.33}(Mn_{1-x}Co_x)O_3

76%
Mihalik M., Kavečanský V., Maťaš S., Zentková M., Ammer J., Kellner K., Gritzner G.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
251-254
EN
Detailed studies of temperature dependences of magnetization, AC susceptibility and electrical resistance were performed on La_{0.67}Pb_{0.33}(Mn_{1-x}Co_x)O_3 ceramics with x = 0.01 and 0.1. Typical features of both compounds are the hysteretic behavior between the zero-field-cooled magnetization regime and the field-cooled magnetization regime, a very weak field dependence of a maximum in zero-field-cooled magnetization and practically no frequency dependence of the peak in AC susceptibility χ"(T). Anomalies in the electrical resistance connected with the ferromagnetic transition at T_C, the insulator-metal transitions at T_p and the re-entrant metal-isolator transition at T* are field dependent pointing to magnetic origin of these transitions. Colossal magnetoresistance was observed in both compounds.
4
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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.
5
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Effect of Pressure on Magnetic Properties of Hexacyanochromates

76%
Mitróvá Z., Maťaš S., Mihalik M., Zentková M., Arnold Z., Kamarád J.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
469-472
EN
We present the study of pressure effect on magnetic properties of TM^{2+}_3[Cr^{III}(CN)_6]_2·nH_2O ferrimagnets and ferromagnets (TM = Cr and Co) under pressures up to 0.9 GPa. Applied pressure strengthens super-exchange interaction in Cr^{2+}-prussian blue analogues with dominant antiferromagnetic interaction J_{AF} leading to increase in the Curie temperature T_C (ΔT_c/Δp = 29.0 K/GPa) and reduces T_C of Co^{2+}-prussian blue analogues with dominant ferromagnetic interaction J_F (ΔT_c/Δp = -1.8 K/GPa). The rise of J_{AF} interaction is attributed to the enhanced value of the single electron overlapping integral S. On the other hand, the applied pressure slightly affects bonding angles between magnetic ions mediated by the cyano-bridge and reduces the strength of magnetic coupling. Changes of the magnetization curve with pressure can be attributed to changes of magnetic anisotropy. The reduction of magnetization with pressure observed on Cr^{2+}-prussian blue analogues can be explained by pressure induced transition from Cr^{2+} high spin state to Cr^{2+} low spin state. All pressure induced changes are reversible.
6
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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.
7
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Magnetic Properties of Milled and Thermal Relaxed YBa_{2} (Cu_{1-x}Fe_{x})_{3}O_{y}

76%
Timko M., Kováč J., Sargánková I., Zentková M., Mihalik M., Maťaš S., Čiasnohová A.
Acta Physica Polonica A
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1997
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vol. 91
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issue 2
355-358
EN
The influence of the mechanical milling and subsequent thermal relaxation on magnetic and superconducting behaviour of YBa_{2}(Cu_{1-x}Fe _{x})_{3}O_{y} system has been studied. Two methods of heat treatment were used: Set I - slow cooling from 980°C in flowing O_{2} and Set II - reducing at 770°C in flowing Ar_{2} followed by reoxidation in flowing O_{2} below 400°C. The transition to superconductivity, diamagnetic response, critical current density and the effective magnetic moment in the normal state have been estimated. Our measurements indicate that the reducing atmosphere preparation is less detrimental on superconducting properties. The results are discussed in terms of occupancy Cu sites by Fe and redistribution of oxygen atoms.
8
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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.
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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.
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vol. 126
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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.
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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.
11
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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.
12
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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.
13
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Magnetic Relaxation and Memory Effect in Nickel-Chromium Cyanide Nanoparticles

64%
Zentko A., Kavečanský V., Mihalik M., Maťaš S., Mitróová Z., Zentková M., Maryško M., Jagličić Z.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
511-514
EN
The low temperature dynamics of a magnetic nanoparticle system Ni_3[Cr(CN)_6]_2 with an average nanoparticles size of 4 nm was studied. Using different temperature and field protocols memory phenomena were studied by the DC magnetization and magnetic relaxation measurements of the system at temperatures below T_m = 19 K. Aging experiments show an absence of any waiting time dependence in the magnetization relaxation due to a field change after zero field and field cooling. This observation discriminates the dynamics of the system from the behaviour of a classical spin-glass.
14
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Effect of Pressure on Magnetic Properties of TM_3[Cr(CN)_6]_2 · nH_2O Nanoparticles

64%
Zentko A., Zentková M., Kavečanský V., Mihalik M., Mitróová Z., Arnold Z., Kamarád J., Cieslar M., Zeleňák V.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
489-493
EN
Effect of pressure on magnetic properties of magnetic nanoparticles, based on Prussian blue analogues, were studied in pressures up to 1.2 GPa. The Mn_3[Cr(CN)_6]_2·nH_2O and Ni_3[Cr(CN)_6]_2·nH_2O nanoparticles were prepared by reverse micelle technique. Transmission electron microscopy images show nanoparticles with average diameter of about 3.5 nm embedded in an organic matrix. The characteristic X-ray peaks of nanoparticles are more diffused and broader. Systems of nanoparticles behave as systems of interacting magnetic particles. The Curie temperature T_C is reduced from T_C = 56 K for Ni-Prussian blue analogues to T_C = 21 K for Ni-nanoparticles system and from T_C = 65 K for Mn-Prussian blue analogues to T_C = 38 K for Mn-nanoparticles system. One can explain this reduction of the Curie temperature and of the saturated magnetizationμ_s by dispersion of nanoparticles in an organic matrix i.e. by a dilution effect. Applied pressure leads to a remarkable increase in T_C for system of Mn-nanoparticles (ΔT_C/Δp = +13 K/GPa) and to only slight decrease in T_C for system of Ni-nanoparticles (ΔT_C/Δp = -3 K/GPa). The pressure effect follows behavior of the mother Prussian blue analogues under pressure. The increase in saturated magnetization, attributed to compression of the organic matrix, is very small.
15
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^1H NMR on (Ni_xMn_{1-x})_3[Cr(CN)_6]_2 · nH_2O

64%
Bokor M., Tompa K., Kiss L., Zentková M., Zentko A., Mihalik M., Maťaš S., Mitróová Z.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
485-488
EN
We report on ^1H NMR of (Ni_xMn_{1-x})3[Cr(CN)_6]_2·15H_2O hexacyanochromates, where x changes from 0 to 1. The decay time constants of the free induction decay signals described by an effective spin-spin relaxation time T_{2eff} obtained from M(t) = M_0 exp(t/T_{2eff}) decrease as the local magnetic moments increase produced by the magnetic transition metal ions at the sites of the resonant ^1H nuclei. The recovery of the magnetization in the spin-lattice relaxation time (T_1) experiments was single-exponential.
16
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Effect of Pressure on Magnetic Properties of (NH_3OH)_2CoF_4 Fluoro-Metal Complex

64%
Jagličić Z., Zentková M., Mihalik M., Drofenik M., Kristl M., Dojer B., Kasunič M., Golobič A., Jagodič M., Arnold Z.
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issue 5
1074-1075
EN
Effect of pressure on magnetic properties of a bulk fluoro-metal complex (NH_3OH)_2MF_4 was studied. Magnetization measurements suggest that a ferromagnetic transition at T_{C1} = 47 K is followed by a ferrimagnetic one at T_{C2} = 3 K. Both transition temperatures are pressure dependent with the pressure coefficients dT_{C1}/ dp = - 2.6 K/GPa and dT_{C2}/ dp = 0.26 K/GPa. The opposite sign of the coefficients is an additional indication of a different nature (ferromagnetic/antiferromagnetic) of these two transitions. The effect of pressure on low field magnetization and exchange bias phenomena is small but still visible.
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