We systematically investigate three body-centred cubic (bcc) high-entropy alloys (HEAs) with an identical valence electron count (VEC = 4.375): (NbHf)0.75(TiZr)0.25, (NbZr)0.75(TiHf)0.25, and (NbTi)0.75(ZrHf)0.25. Despite their isoelectronic nature, it was found that these alloys exhibit markedly different superconducting properties. Critical temperatures Tc range from 7.14(5) K to 8.17(5) K, while upper critical fields μ0Hc2(0) exceed 12 T, reaching 14.0(9) T for the Ti-rich alloy (NbTi)0.75(ZrHf)0.25. These variations highlight the limited predictive power of the Matthias rule in HEA design. Furthermore, the exceptional properties observed in the Ti-rich composition suggest that Nb and Ti are critical elements for the development of new HEAs for next-generation superconducting magnets.

Physical and structural properties of two high-entropy alloys (HEA), Ti0.5(ZrNbHfTa)0.5 and Ti0.5(VNbHfTa)0.5, belonging to the new type of Ti-rich HEA were studied by powder x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDXS), magnetization, electrical resistivity and specific heat measurements. The experimental results were supported by theoretical calculations of the electronic structure using projector augmented wave (PAW) within the density functional theory. Simulated structure relaxations with several degrees of freedom were applied to calculate the total density of states. It was found that both alloys are crystallizing in the bcc structure (space group Im3m, W-type structure) despite the fact that they are formed in 75 and 62.5 at.% from elements crystallizing in hexagonal structure. The presence of minor stoichiometric variations in the samples was detected by EDXS mapping, but its effect on the physical properties seemed negligible. At low temperatures, the alloys become type II superconductors, with a critical temperature in the range of 5.9 - 6.0 K and an upper critical field reaching 13.5 T, a value that is exceptionally high for HEA

Superconducting alloy containing terbium (Tb) and its reference without the lanthanide were synthesized. X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, specific heat, and magnetic measurements were used to investigate their structural and physical properties. Both alloys crystallized in body-centered cubic structure, and the presence of small amounts of Tb and Tb2O3 phases was detected. The critical temperature Tc of alloys was in the 4.6-5.2 K range, and the upper critical field μ0Hc2 was 6.1-6.8 T. The comparison with the reference determined the effect of Tb on the alloy's critical parameters and phase stability connected to the high-entropy alloys' core effects. Overall, Tb addition did not have a beneficial effect on the superconducting properties of this alloy.

CeRh_{2}As_{2} is rare among superconductors, in that the magnetic field tunes it between two distinct superconducting phases. Combined with a lack of local inversion symmetry and an upper critical field exceeding the Pauli paramagnetic limit, this excitingly suggests triplet multicomponent superconductivity. Preceding the superconducting onset, f-electron correlations cause long-range order, attributed both to local antiferromagnetism and itinerant (quadrupole) density waves. A magnetic field provides a significant perturbation of the f electrons and may reveal the nature of the many-body correlations. Therefore, we report comprehensive magnetization and magnetotransport studies on microstructured devices in fields of up to 73 T. Applied along the c axis, the field causes a low-temperature change of majority (hole) carrier density at μ_{0}H≈24 T. By contrast, in-plane fields produce a cascade of phase transitions; the field-induced in-plane conductivity anisotropy and lack of accompanying magnetic features, plus the closed-dome nature of the overall phase boundary is consistent with a hierarchy of field-induced density-wave states.

The paper describes the physical and structural properties of UNbTiVZr, a novel equimolar type-A high-entropy alloy (HEA) superconductor containing uranium. To our knowledge, only one prior study has reported a nonequimolar uranium-containing HEA, making UNbTiVZr the first equimolar system of this kind. The alloy was characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, electrical resistivity, magnetization and specific heat measurements. It has been determined that the alloy exhibits type II superconductivity, with a critical temperature of about 2 K and an anomalously high upper critical field, for the description of which the Werthamer-Helfand-Hohenber model, modified by the diffusivity distribution, was used.

We synthesized high-quality single crystals of T3In7, T = Ni, Pd, Pt, which crystallize in a body-centered-cubic Im-3m space group with T-metal-based dumbbells. The systematic study of electrical resistivity exhibits metallic behavior with extremely large nonsaturating magnetoresistance reaching 1500% at 14 T with profound Shubnikov-de Hass quantum oscillations. The fast Fourier transformation analysis shows multiple frequencies pointing to a complex structure of the Fermi surfaces. The large magnetoresistance is attributed to the presence of small, closed Fermi surfaces with light cyclotron masses with good agreement with theoretical calculations. We present the first experimental and theoretical study of the Fermi surface in the T3In7 family.

The medium-entropy alloy (NbTa) _0.67 (HfZr) _0.33 and the high-entropy alloy (NbTa) _0.67 (HfZrTi) _0.33 were prepared by mechanical alloying using high-energy planetary ball mill. The results of X-ray diffraction, scanning electron microscopy, and positron annihilation lifetime spectroscopy measurements suggest that both as-prepared powders are multicomponent alloys in amorphous (or highly disordered) state. The magnetic and thermodynamic results obtained for these powders undoubtedly prove that bulk superconductivity is not observed at temperatures exceeding 2 K. Thermal treatment of both studied materials leads to decomposition of the amorphous phase and precipitation of several crystalline phases. In both annealed samples, the structure of the main crystalline phase was identified as body-centered cubic (bcc), and in this phase, bulk superconductivity was observed below 6.5 K.

The specific heat of thermally reduced graphene oxide (trGO) was measured by a thermal relaxation method in the temperature range from 0.3 to 275 K. It was found that the temperature dependence of the heat capacity С(Т)/T vs T2 of trGO is nonmonotonic. It has been established that in the temperature range of 0.3–6 K there is an anomalous behavior of the temperature dependence of the heat capacity trGO, sharply changing its character. It is assumed that this anomaly is due to the influence of impurities and defects, structural features.

The medium-entropy alloy (NbTa)(0.67)(HfZr)(0.33 )and the high-entropy alloy (NbTa)(0.67)(HfZrTi)(0.33) were prepared by mechanical alloying using high-energy planetary ball mill. The results of X-ray diffraction, scanning electron microscopy, and positron annihilation lifetime spectroscopy measurements suggest that both as-prepared powders are multicomponent alloys in amorphous (or highly disordered) state. The magnetic and thermodynamic results obtained for these powders undoubtedly prove that bulk superconductivity is not observed at temperatures exceeding 2 K. Thermal treatment of both studied materials leads to decomposition of the amorphous phase and precipitation of several crystalline phases. In both annealed samples, the structure of the main crystalline phase was identified as body-centered cubic (bcc), and in this phase, bulk superconductivity was observed below 6.5 K.

The mystery of the field-independent T 1/2 / 2 behavior of resistivity in single-crystal Th2CoSi3 2 CoSi 3 is unraveled through the lens of interacting electrons in disordered systems. Consistent with theoretical predictions, our magnetotransport studies illuminate a scenario where a robust spin-orbit interaction renders the triplet term in the diffusion contribution ineffective. As a consequence, the magnetic field exerts no influence on the diffusion correction, giving sole dominance to weak localization and classical effects in shaping the magnetoresistance. In addition, marginal temperature variation of the weak localization at low temperatures results in the T 1/2 / 2 relation being predominantly dictated by the singlet term in the diffusion correction.

Th-containing superconducting high entropy system with the nominal composition (NbTa) _0.67 (MoWTh) _0.33 was synthesized. Its structural and physical properties were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, specific heat, resistivity and magnetic measurements. Two main phases of alloy were observed: major bcc structure and minor fcc. The experimental results were supported by numerical simulation by the DFT Korringa-Kohn-Rostoker method with the coherent potential approximation (KKR-CPA).

The locally noncentrosymmetric ferromagnet URhGe2, which undergoes ordering at the Curie temperature T-C=25 K, was subjected to a comprehensive investigation employing x-ray diffraction, magnetic susceptibility, electrical resistivity, and specific heat measurements. Our results reveal a significant heat capacity anomaly in the paramagnetic state near 30 K which is due to two simultaneous phase transitions characterized by temperatures T-s similar or equal to 29.5 K and T-m similar or equal to 30 K. In particular, with increasing applied magnetic field, T-m shifts to higher temperatures, while T-s remains unaffected, suggesting a different nature of these transitions and leading to a complex temperature-magnetic field phase diagram. The field-independent phase transition can be interpreted in terms of structural distortions, while the second transition defies typical behavior for ferro- or antiferromagnetic phases, suggesting a more intricate magnetic structure or multipole ordering. The electron transport shows strong anisotropy, not only in the magnitude of the resistivity but also in its temperature dependence. The three times higher residual resistivity along the crystallographic c axis, compared to the a axis component significantly influences its temperature dependence. While the a-axis resistivity behaves typically for normal ferromagnets, the c-axis resistivity shows a minimum in its temperature dependence well below T-C. This behavior results from the competition between electron spin wave scattering and quantum corrections, dominated by the A(QC)T(1/2 )contribution due to impurity scattering assisted electron-electron interaction. Remarkably, the A(QC)T(1/2 )dependence with a comparable A(QC) coefficient is also observed for T >> T-C, indicating the relevance of interaction quantum effects in electron transport also in the paramagnetic state.

Temperature and magnetic field dependencies of resistance for functionalized multiwall carbon nanotubes (MWCNTs) have been studied. The measurements were carried out in the temperature range T = 4.2–200 K. It is shown that in magnetic fields up to B = 9 T, the conductivity behavior for the functionalized MWCNTs sample can be described in terms of charge carriers weak localization and interaction phenomena. We show that the contribution to the functionalized MWCNTs conductivity due to the weak localization effect exceeds the quantum correction due to the effect of the charge carriers interaction for all the temperatures and in the entire range of the applied magnetic fields except for the magnetic fields above B = 6.5 T at T = 5 K. Within the terms of the specified models, we estimate the value of the Fermi energy and determine the explicit form of the temperature dependence of the phase relaxation time for the wave function. We show that for the functionalized MWCNTs sample, the phase relaxation time for the wave function has a less pronounced temperature dependence, and its Fermi energy is more shifted to the valence band compared to non-functionalized MWCNTs. The charge carriers’ interaction constant at different temperatures can also be estimated from our experiments.

Single crystals of the compound Ce3PdIn11 that belongs to a large family of superconducting cerium indides with the general formula Ce m T n In3m +2n (T stands for d-electron transition metal) were grown from indium flux and characterized by means of low-temperature specific heat and electrical resisitivity measurements. The collected data revealed significant sample-dependent divergence in their magnetic and superconducting properties which raises the question of whether these two cooperative phenomena are intrinsic properties of Ce3PdIn11.

Polycrystalline samples of novel compounds Ce0.67Pd2Al5, Ce1.33Pd3Al8, and Ce1.74Pd5.29Al11.71 were prepared by arc-melting. The crystal structure of the latter compound was determined from the single-crystal X-ray diffraction data to be a disordered variant of the hexagonal Th2Ni17 type [P6(3)/mmc, a = 9.1961(5) angstrom, c = 8.8861(5) angstrom]. The crystal structures of the other aluminides were examined by powder X-ray diffraction and found to be isotypic with Sc0.67Fe2Si5 [P63/mmc, a = 4.3385(5) angstrom, c = 16.5255(15) angstrom] and Gd1.33Pt3Al8 [R (3) over barm, a = 4.37960(10) angstrom, c = 39.1683(9) angstrom], respectively. Based on the thermodynamic and electrical resistivity data measured down to 0.4 K in external magnetic fields up to 9 T, the new materials were characterized as metallic Curie-Weiss paramagnets due to fairly stable trivalent Ce ions. In Ce1.33Pd3Al8, an antiferromagnetic ordering was established below T-N = 2.3 K, while no long-range magnetic order was found in the other compounds. All three phases exhibit electrical conductivity that is governed by the interplay of Kondo and crystalline electric field interactions, and significantly affected by structural disorder inherent to their crystal lattices. (C) 2022 Elsevier B.V. All rights reserved.

The magnetoresistance of multi-walled carbon nanotubes is studied in the temperature range 4.2–200 K and magnetic fields up to 9 T. The magnetoresistance is negative in the whole temperature range. For small magnetic fields and low temperatures, the dependence of the relative conductivity on the magnetic field is quadratic. However, as the magnetic field increases, it becomes logarithmic, which may be described by weak localization and charge carriers’ interaction models. We show that the addition to conductivity due to the charge carriers’ weak localization significantly exceeds the addition due to the effect of the charge carriers’ interaction. The Fermi energy and the charge carriers’ interaction constant were estimated in terms of these models using the experimental data on the magnetoresistance field and temperature dependences. Also, we determined the exact form for the temperature dependence of the phase relaxation time of the charge carriers’ wave function.

The electrical transport in the half-Heusler phases LuNiSb and YPdSb was measured in a temperature range 2-300 K. For both compounds, the electrical resistivity was found to decrease with increasing temperature, showing a linear-in-T behavior over an extended temperature interval. In order to interpret the experimental data, a two-channel conductivity model was applied, which revealed that not only the semiconducting-like transport but also the metallic-like one exhibit negative temperature coefficients. The unusual behavior in the metallic channel was described within the Cote-Meisel formalism based on the diffraction model of strongly disordered metals. In addition, a weak localization scenario was considered including spin-orbit scattering and Coulomb interaction between conducting electrons. The electron-electron interaction was found most important at the lowest temperatures, where the semiconducting channel becomes ineffective, reminiscent of charge transport confined to a narrow yet finite-size metallic band located inside the semiconducting energy gap. The low-temperature resistivity of YPdSb appeared fully describable in terms of the Altshuler-Aronov quantum correction due to interacting electrons. In turn, the electronic transport in LuNiSb was found affected by the Kondo effect associated with a small amount of paramagnetic impurities present in the specimen investigated. The approach developed for LuNiSb and YPdSb can be applied to other half-Heusler compounds that exhibit atom disorder in their crystal structures.

We report on the synthesis of polycrystalline samples of heavy-fermion compound Ce3PtIn11 and the characterization of their structural and low-temperature physical properties. In good agreement with the data previously obtained for single crystals, the polycrystals also form with a tetragonal crystal structure (space group P4/mmm, Z = 1) with the lattice parameters a = b = 4.6934(7) angstrom, and c = 16.8306(3) angstrom. Alike the single crystals, they exhibit two successive antiferromagnetic phase transitions at T-N1 = 2.16 K and T-N2 = 2.0 K, followed by a superconducting transition at T-c = 0.33 K. Our findings open new opportunities for comprehensive investigations of the interplay between magnetism and superconductivity in Ce3PtIn11 by means of experimental techniques which usually require bulky specimens.

R. Kurleto,1 M. Fidrysiak,2 L. Nicolaï,3 J. Minár,3 M. Rosmus,1, 4 Ł. Walczak,5 A. Tejeda,6 J. E. Rault,7 F. Bertran,7 A. P. Kądzielawa,8, 2 D. Legut,8 D. Gnida,9 D. Kaczorowski,9 K. Kissner,10 F. Reinert,10 J. Spałek,2 and P. Starowicz1 Marian Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków, Poland Institute of Theoretical Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków, Poland New Technologies-Research Center, University of West Bohemia, Univerzitní 8, 306 14 Pilsen, Czech Republic Solaris National Synchrotron Radiation Centre, Jagiellonian University, Czerwone Maki 98, 30-392 Kraków, Poland PREVAC sp. z o.o., Raciborska 61, PL-44362 Rogów, Poland Laboratoire de Physique des Solides, CNRS, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay, France Synchrotron-SOLEIL, Saint-Aubin, BP48, F91192 Gif sur Yvette Cedex, France IT4Innovations, VŠB Technical University of Ostrava, 17. listopadu 2172/15, 708 00 Ostrava-Poruba, Czech Republic Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wrocław, Poland Experimentelle Physik VII and Würzburg-Dresden Cluster of Excellence ct.qmat, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany (Dated: September 7, 2021)

We report point-contact spectroscopy measurements on heavy fermion cousins CeCoIn5, Ce2PdIn8 and Ce3PdIn11 to systematically study the hybridization between f and conduction electrons. Below a temperature T*, the spectrum of each compound exhibits an evolving Fano-like conductance shape, superimposed on a sloping background, that suggests the development of hybridization between local f and itinerant conduction electrons in the coherent heavy fermion state below T*. We present a quantitative analysis of the conductance curves with a two-channel model to compare the tunneling process between normal metallic silver particles in our soft point-contact and heavy-fermion single crystals CeCoIn5, Ce2PdIn8 and Ce3PdIn11.