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1

Superconductivity of Niobium Thin Films in the BiOCl/Nb Heterostructures

100%

Lotnyk D., Komanický V., Bunda V., Feher A.

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EN

In the current paper, electrical transport properties of 25 nm thick Nb films sputtered on the photosensitive semiconductor BiOCl were investigated in the temperature range 7.5 K ≤ T ≤8.5 K. The influence of green (532 nm) and red (640 nm) laser excitations on resistive superconducting transitions of the niobium thin films on a silicon glass and BiOCl single crystal substrates were studied. The temperature dependences of the resistivity for Nb are in good agreement with the McMillan model which indicates the strong influence of the inverse proximity effect induced by the interface. The increased influence of the BiOCl/Nb interface under laser excitation corresponds to the raising of the ratio of the density of normal to superconductivity carriers in the Tıghtarrow0 limit and this observation is in agreement with the photoconductivity study of BiOCl single crystals.

2

Study of Niobium Thin Films under Pressure

88%

Pristáš G., Gabáni S., Orendáč M., Komanický V., Gažo E.

Acta Physica Polonica A

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2014

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vol. 126

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issue 1

346-347

EN

Niobium is widely used in many important superconducting applications. At ambient pressure, bulk Nb has the highest critical temperature, T_c ≈ 9.25 K among the superconducting elements. Thin films of Nb show several differences in behavior in comparison with bulk Nb, e.g. substantial increase in the upper critical field (H_{C2}). Critical temperature of superconducting transition is usually lower for thin films than in bulk sample and depends on thickness of the film, size of grains etc. We prepared 100 nm thick niobium thin films in the high vacuum DC magnetron sputtering system, with T_c=8.95 K at ambient pressure. In this study, we performed measurements of superconducting transition temperature by electrical resistivity measurements of Nb thin film under hydrostatic pressure of up to 30 kbar. We observed an increase of T_c with increasing value of pressure (dT_c/dp=7.3 mK/kbar). On the other side in the case of bulk sample of Nb we observed a decrease of T_c value (dT_c/dp=-2.5 mK/kbar) with increasing applied pressure. Difference in superconducting properties between niobium bulk and thin film under pressure is discussed.

3

Magnetic and Structural Characterization of Nickel and Iron Based Heusler Ribbons Ni₂FeZ (Z = In, Sn, Sb)

76%

Frol'ová L., Ryba T., Vargová Z., Komanický V., Kováč J., Gyepes R., Varga R.

Acta Physica Polonica A

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2017

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vol. 131

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issue 4

735-737

EN

Comparison of structural, chemical, and magnetic properties of Ni₂FeZ (Z = In, Sn, Sb) Heusler ribbons produced by melt-spinning method is presented. The aim of work was to prepare the Heusler alloys with the appropriate chemical composition in a single step without additional thermal treatment. Scanning electron microscopy analysis revealed polycrystalline structure of all samples. It is shown that correct L2₁ structure of Ni₂FeSb can be obtained in a single production step. On the other hand, no Heusler L2₁ phase (nor its variants) occur in Ni₂FeSn alloy. Additionally, magnetic characterization revealed high Curie temperatures of the Heusler phases (above 600 K for Ni₂FeSb and 800 K for Ni₂FeIn).

4

Specific Heat Study of Superconductivity in Cu_{0.061}TiSe_{2}

76%

Kačmarčík J., Pribulová Z., Pal'uchová V., Husaníková P., Karapetrov G., Komanický V., Samuely P.

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EN

In TiSe_{2} a charge-density-waves order is continuously suppressed by copper doping and superconductivity appears. We report a calorimetric study performed on the superconducting single crystal of Cu_{0.061}TiSe_{2} with T_{c}=2.8 K, measured by the ac technique at low temperatures down to 0.6 K and magnetic fields up to 2 T. Sharp specific heat anomaly at the superconducting transition is found. The temperature dependence of the electronic specific heat and the angular dependence of the critical temperature, measured at a fixed magnetic field, consistently indicate on the existence of a single s-wave superconducting gap with a coupling strength of 2Δ/k_{B}T_{c}=3.6, close to BCS limit.

5

Growth of Pt-Ni Nanoparticles of Different Composition using Electrodeposition and Characterization of Their Magnetic Properties

76%

Kožejová M., Hložná D., Hua Liu Y., Ráczová K., Čižmár E., Orendáč M., Komanický V.

Acta Physica Polonica A

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2017

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vol. 131

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issue 4

839-841

EN

We prepared Pt₃Ni and PtNi₃ nanoparticles of various sizes on conductive and atomically smooth highly oriented pyrolytic graphite surfaces using potentiostatic electrodeposition. We can control the size of electrodeposited nanoparticles and their density on the surface by changing the deposition time. The morphology of nanoparticles was determined by scanning electron microscopy. PtNi₃ particles have spherical shape, while Pt₃Ni particles have more irregular shape. Composition of particles was confirmed by energy dispersive spectroscopy. We have measured magnetic properties of both systems with 100 s preparation time, superparamagnetic behavior was observed in PtNi₃ nanoparticles with blocking temperature T_{B}=225 K.

6

Enhanced Superconductivity in Nanosized Tips of Scanning Tunnelling Microscope

76%

Samuely T., Szabó P., Komanický V., Rodrigo J., Vieira S., Samuely P.

Acta Physica Polonica A

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2010

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vol. 118

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issue 5

1038-1039

EN

Nanosized Pb junctions exhibit superconducting correlations at magnetic fields more than an order of magnitude higher than the zero-temperature critical field of the bulk Pb. The strongly enhanced critical field is a spectacular demonstration of nanosize effect where the Meissner screening currents become ineffective for junction's tip smaller than the London penetration depth (32 nm for Pb). From the enhanced critical field we characterize the geometry of a particular junction using the variable radius pair breaking theoretical model of Suderow et al.

7

Local Magnetometry of Cu_{0.064}TiSe_{2}

64%

Pribulová Z., Medvecká Z., Kačmarčík J., Komanický V., Klein T., Husaníková P., Cambel V., Šoltýs J., Karapetrov G., Samuely P.

Acta Physica Polonica A

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2014

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vol. 126

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issue 1

370-371

EN

Local magnetometry using miniature Hall-probe array was used to study vortex distribution in superconducting single crystal of Cu_{x}TiSe_{2}, with x=0.064 and T_{c}=3.2 K. We show that vortices after penetration into the sample move towards the center, resulting into a dome-shape field profile. Such a profile is a signature of relatively low pinning. We show that these measured profiles are consistent with a model proposed for the samples in the absence of bulk pinning. Modifications necessary to obtain quantitative agreement between the model and the data are presented.

Refine search results

Superconductivity of Niobium Thin Films in the BiOCl/Nb Heterostructures

Study of Niobium Thin Films under Pressure

Magnetic and Structural Characterization of Nickel and Iron Based Heusler Ribbons Ni₂FeZ (Z = In, Sn, Sb)

Specific Heat Study of Superconductivity in Cu_{0.061}TiSe_{2}

Growth of Pt-Ni Nanoparticles of Different Composition using Electrodeposition and Characterization of Their Magnetic Properties

Enhanced Superconductivity in Nanosized Tips of Scanning Tunnelling Microscope

Local Magnetometry of Cu_{0.064}TiSe_{2}