Publications de Janusz Andrzej Karpinski

Single crystals of superconducting SmFeAsOHx: Structure and properties

László Forró, Richard Gaal, Alla Arakcheeva, Sergiy Katrych, Janusz Andrzej Karpinski, Andrea Pisoni, Ping Huang, Péter Krisztián Matus

We report the synthesis, structure, and superconducting properties of single crystals of SmFeAsOHx. The crystals were grown at high pressure and high temperature using a cubic anvil technique. H-1-NMR studies confirm the presence of H atoms in the samples. ...

Amer Physical Soc2016

Upper critical field, pressure-dependent superconductivity and electronic anisotropy of Sm4Fe2As2Te1-xO4-yFy

László Forró, Richard Gaal, Bálint Náfrádi, Sergiy Katrych, Janusz Andrzej Karpinski, Andrea Pisoni, Péter Szirmai

We present a detailed study of the electrical transport properties of a recently discovered iron-based superconductor: Sm4Fe2As2Te0.72O2.8F1.2. We followed the temperature dependence of the upper critical field by resistivity measurement of single crystals ...

Iop Publishing Ltd2016

Magnetotransport studies of superconducting Pr4Fe2As2Te1-xO4

László Forró, Richard Gaal, Bálint Náfrádi, Sergiy Katrych, Janusz Andrzej Karpinski, Andrea Pisoni, Péter Szirmai

We report a study of the electrical transport properties of single crystals of Pr(4)Fe(2)As(2)Te(1-)xO(4), a recently discovered iron-based superconductor. Resistivity, Hall effect, and magnetoresistance are measured in a broad temperature range revealing ...

Amer Physical Soc2016

Local lattice distortions vs. structural phase transition in NdFeAsO1-xFx

Sergiy Katrych, Janusz Andrzej Karpinski

The lattice properties at low temperatures of two samples of NdFeAsO1-xFx (x = 0.05 and 0.25) have been examined in order to investigate possible structural phase transition that may occur in the optimally doped superconducting sample with respect to the n ...

Elsevier2016

Inhomogeneity of charge-density-wave order and quenched disorder in a high-T-c superconductor

Janusz Andrzej Karpinski, Davide Innocenti

It has recently been established that the high-transition-temperature (high-T-c) superconducting state coexists with short-range charge-density-wave order(1-11) and quenched disorder(12,13) arising from dopants and strain(14-17). This complex, multiscale p ...

Nature Publishing Group2015

Mossbauer studies of the peculiar magnetism in parent compounds of the iron-based superconductors

Janusz Andrzej Karpinski

A review of the magnetism in the parent compounds of the iron-based superconductors is given based on the transmission Mossbauer spectroscopy of Fe-57 and Eu-151. It was found that the 3d magnetism is of the itinerant character with varying admixture of th ...

Taylor & Francis Ltd2015

Measurement of the penetration depth and coherence length of MgB2 in all directions using transmission electron microscopy

Janusz Andrzej Karpinski

We demonstrate that images of flux vortices in a superconductor taken with a transmission electron microscope can be used to measure the penetration depth and coherence length in all directions at the same temperature and magnetic field. This is particular ...

Amer Physical Soc2015

Slow magnetic fluctuations and superconductivity in fluorine-doped NdFeAsO

Sergiy Katrych, Janusz Andrzej Karpinski

Among the widely studied superconducting iron-pnictide compounds belonging to the Ln1111 family (with Ln a lanthanide), a systematic investigation of the crossover region between the superconducting and the antifer-romagnetic phase for the Ln = Nd case has ...

Amer Physical Soc2015

Critical current anisotropy in Nd-1111 single crystals and the influence of neutron irradiation

Sergiy Katrych, Janusz Andrzej Karpinski

We report on angle-resolved magnetization measurements on NdFeAsO0.65F0.35 ( Nd-1111) single crystals. The field dependence of the critical current density, Jc, is non-monotonic in these crystals at all orientations and temperatures due to the fishtail eff ...

Iop Publishing Ltd2014

Electric field gradient wave (EFGW) in iron-based superconductor Ba0.6K0.4Fe2As2 studied by Mossbauer spectroscopy

Janusz Andrzej Karpinski

The optimally doped '122' iron-based superconductor Ba0.6K0.4Fe2As2 has been studied by Fe-57 Mossbauer spectroscopy versus temperature ranging from 4.2 K till 300 K with particular attention paid to the superconducting transition around 38 K. The spectra ...

Elsevier Science Sa2014

Magnetic field penetration in MgB2 single crystals: Pinning and Meissner holes

Sergiy Katrych, Janusz Andrzej Karpinski

The evolution of flux distribution in MgB2 single crystals during their remagnetization was imaged with magneto-optical technique. Meissner holes, formed as the areas where the annihilation of vortices and antivortices takes place, were found at the bounda ...

Amer Inst Physics2014

L4Fe2As2Te1-xO4-yFy (L = Pr, Sm, Gd): A layered oxypnictide superconductor with T-c up to 45 K

László Forró, Richard Gaal, Sergiy Katrych, Janusz Andrzej Karpinski, Andrea Pisoni

The synthesis and structural and physical properties of iron lanthanide oxypnictide superconductors, L4Fe2As2Te1-xO4 (L = Pr, Sm, Gd), with transition temperature at similar to 25 K are reported. Single crystals have been grown at high pressure using the c ...

Amer Physical Soc2014

Huge critical current density and tailored superconducting anisotropy in SmFeAsO0.8F0.15 by low-density columnar-defect incorporation

Sergiy Katrych, Janusz Andrzej Karpinski, Yihan Jia

Iron-based superconductors could be useful for electricity distribution and superconducting magnet applications because of their relatively high critical current densities and upper critical fields. SmFeAsO0.8F0.15 is of particular interest as it has the h ...

Nature Publishing Group2013

Quantitative imaging of flux vortices in the type-II superconductor MgB2 using cryo-Lorentz transmission electron microscopy

Marco Cantoni, Mathieu Julien Gino Cottet, Cécile Hébert, Duncan Thomas Lindsay Alexander, Fabrizio Carbone, Janusz Andrzej Karpinski

Imaging of flux vortices in high quality MgB2 single crystals has been successfully performed in a commercial field-emission gun-based transmission electron microscope. In cryo-Lorentz microscopy, the sample quality and the vortex lattice can be monitored ...

Amer Physical Soc2013

The Order-Parameter Symmetry and Fermi Surface Topology of 122 Fe-Based Superconductors: A Point-Contact Andreev-Reflection Study

Janusz Andrzej Karpinski

We report on the results of directional point-contact Andreev-reflection (PCAR) measurements in Ba(Fe1-x Co (x) )(2)As-2 single crystals and epitaxial c-axis oriented films with x=0.08 as well as in Ca(Fe1-x Co (x) )(2)As-2 single crystals with x=0.06. The ...

Springer2013

Pr4Fe2As2Te1-xO4: A layered FeAs-based superconductor

László Forró, Richard Gaal, Sergiy Katrych, Janusz Andrzej Karpinski, Andrea Pisoni

We report crystal growth at high pressure, structure determination, and magnetic and transport studies of an oxypnictide superconductor Pr4Fe2As2Te1-xO4. Its structure resembles the known 1111 phase except for the considerably larger c lattice constant and ...

Amer Physical Soc2013

Persistence of Metastable Vortex Lattice Domains in MgB2 in the Presence of Vortex Motion

Janusz Andrzej Karpinski

Recently, extensive vortex lattice metastability was reported in MgB2 in connection with a second-order rotational phase transition. However, the mechanism responsible for these well-ordered metastable vortex lattice phases is not well understood. Using sm ...

Amer Physical Soc2013

Normal state bottleneck and nematic fluctuations from femtosecond quasiparticle relaxation dynamics in Sm(Fe,Co)AsO

Janusz Andrzej Karpinski

We investigate temperature and fluence dependent dynamics of the photoexcited quasiparticle relaxation and low-energy electronic structure in electron-doped 1111-structure Sm(Fe0.93Co0.07)AsO single crystal. We find that the behavior is qualitatively ident ...

Amer Physical Soc2013

Bulk Electronic Structure of Superconducting LaRu2P2 Single Crystals Measured by Soft-X-Ray Angle-Resolved Photoemission Spectroscopy

Joël Mesot, Elia Razzoli, Johan Juul Chang, Janusz Andrzej Karpinski, Thorsten Schmitt

We present a soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) study of the stoichiometric pnictide superconductor LaRu2P2. The observed electronic structure is in good agreement with density functional theory (DFT) calculations. However, it ...

2012

Matthiessen's rule in MgB2: Resistivity and T-c as a function of point defect concentration

László Forró, Richard Gaal, Neven Barisic, Balazs Sipos, Janusz Andrzej Karpinski

We present the results of a systematic study of the temperature-dependent resistivity and of T-c of a single crystal MgB2 sample as a function of point defect concentration. We have found linear, albeit weak, correlation between the decreasing superconduct ...

2007