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Structural and transport properties in the normal and superconducting states are investigated in a Ca0.8La0.2FeAs2 single crystal with Tc = 27 K, belonging to the newly discovered 112 family of iron based superconductors. The transport critical current density Jc for both field directions measured in a focused ion beam patterned microbridge reveals a weakly field dependent and low anisotropic behaviour with a low temperature value as high as Jc(B = 0) ∼ 105 A/cm2. This demonstrates not only bulk superconductivity but also the potential of 112 superconductors towards applications. Interestingly, this superconducting compound undergoes a structural transition below 100 K which is evidenced by temperature-dependent X-ray diffraction measurements. Data analysis of Hall resistance and magnetoresistivity indicate that magnetotransport properties are largely dominated by an electron band, with a change of regime observed in correspondence of the onset of a structural transition. In the low temperature regime, the contribution of a hole band to transport is suggested, possibly playing a role in determining the superconducting state.

Abstract In this work we will show how it is possible to apply the so called nano-oxidation technique to pattern electrical circuits on oxygen deficient SrTiO3 (STO) thin films. We will focus on two aspects: the chemical reactions which are triggered at the surface of oxygen deficient STO thin films by the voltage biased tip of an atomic force microscope (AFM) and the exploitation of this phenomenology to pattern insulating regions on oxygen deficient STO thin films in the submicron regime. Due to the insulating nature of the AFM modified regions and to the possibility to remove selectively the modified parts, planar electrical circuits entirely designed over STO thin films can be fabricated. A prototype of planar side gate field effect thin film transistor in which STO acts both as active channel and as gate electrode is presented and discussed. [ABSTRACT FROM AUTHOR]

We report a systematic study of the fabrication and chemical and structural characterization of epitaxial Cr films and Pt/Cr bilayers on MgO substrates. Cr films of different thicknesses were grown by molecular beam epitaxy at 373 K and then post-annealed at different temperatures. These films are chemically stable, present a well-ordered tetragonal structure, with only a low degree of oxidation distributed throughout the films. The lattice parameter can be finely tuned by varying the film thickness and the post-annealing temperature, as the elastic energy is progressively relaxed by edge dislocations, so that the film can approach the structural and electrical properties of bulk chromium. Moreover, the chemical and structural properties of Cr are not affected by a Pt capping layer, which grows in a well-ordered Pt[1 1 0]||Cr[1 0 0] orientation, holding potential for applications in recently proposed Pt/Cr-based antiferromagnet spintronics and for the realization of epitaxial Pt films on MgO by using a thin buffer layer of chromium. [ABSTRACT FROM AUTHOR]

In this paper we explore the effects of 3.5 MeV proton irradiation on Fe(Se,Te) thin films grown on CaF2. In particular, we carry out an experimental investigation with different irradiation fluences up to 7.30 · 1016 cm−2 and different proton implantation depths, in order to clarify whether and to what extent the critical current is enhanced or suppressed, what are the effects of irradiation on the critical temperature, resistivity, and critical magnetic fields, and finally what is the role played by the substrate in this context. We find that the effect of irradiation on superconducting properties is generally small compared to the case of other iron-based superconductors. The irradiation effect is more evident on the critical current density Jc, while it is minor on the transition temperature Tc, normal state resistivity ρ, and on the upper critical field Hc2 up to the highest fluences explored in this work. In more detail, our analysis shows that when protons implant in the substrate far from the superconducting film, the critical current can be enhanced up to 50% of the pristine value at 7 T and 12 K; meanwhile, there is no appreciable effect on critical temperature and critical fields together with a slight decrease in resistivity. On the contrary, when the implantation layer is closer to the film–substrate interface, both critical current and temperature show a decrease accompanied by an enhancement of the resistivity and lattice strain. This result evidences that possible modifications induced by irradiation in the substrate may affect the superconducting properties of the film via lattice strain. The robustness of the Fe(Se,Te) system to irradiation-induced damage makes it a promising compound for the fabrication of magnets in high-energy accelerators. [ABSTRACT FROM AUTHOR]

In this work, we investigate the temperature dependence of the upper critical field, dHc2/dT, in an increasingly disordered NdFeAsO0.7F0.3 (NdFeAs(O,F)) single crystal that has been progressively irradiated up to a 5.25 × 1016 cm−2 total α-particle dose. For the H∣∣ab-plane, dHc2/dT does not vary remarkably with irradiation, while for the H∣∣c-axis it increases sharply after the first irradiation of 3.60 × 1015 cm−2 and then more gradually with further irradiation doses. Focusing on the H∣∣c-axis, we develop a phenomenological analysis of the Hc2 slope which allows us to inspect the crossover from the clean to the dirty regime. From the Hc2 slope normalized to the critical temperature and to its clean limit value, we extract the ratio of the coherence length ξBCS to the mean free path and we find that when Tc is reduced by a factor of four from its pristine value, ξBCS/ becomes as large as ∼7 and reaches values of ∼1.8 nm, indicating that NdFeAs(O,F) is well into the dirty regime. Our analysis of the Hc2 slope also allows us to compare the pair-breaking effectiveness of scattering in different superconductors, showing similarity between unconventional NdFeAs(O,F) and moderate-Tc phonon-mediated devices, such as MgB2 and A15 compounds, but much a stronger difference with YBa2Cu3O7-δ. This work thus shows that dHc2/dT is a reliable parameter, providing an alternative to residual resistivity, for investigating the pair-breaking mechanism induced by impurity scattering in superconductors. [ABSTRACT FROM AUTHOR]

In this work we investigate the effect of each different heat treatment stage in the fabrication of Bi2Sr2CaCu2O8+δ superconducting wires on intra-grain and inter-grain superconducting properties. We measure magnetic critical temperature Tc values and transport critical current density Jc at temperatures from 4 K to 40 K and in fields up to 7 T. From an analysis of the temperature dependence of the self-field critical current density Jc(T) that takes into account weak link behavior and the proximity effect, we study grain boundary (GB) transparency to supercurrents; we also establish a relationship between GB oxygenation in the different steps of the fabrication process and GB transparency to supercurrents. We find that GB oxygenation starts in the first crystallization stage, but it becomes complete in the plateau at 836 °C and in slow cooling stages and is further enhanced in the prolonged post-annealing step. Such oxygenation makes GBs more conductive, thus improving the inter-grain Jc value and temperature dependence. On the other hand, from inspection of the Tc values in the framework of the phase diagram dome, we find that grains are already oxygenated in the crystallization step up to the optimal doping, while successive slow cooling and post-annealing treatments further enhance the degree of overdoping, especially if carried out in oxygen atmosphere rather than in air. [ABSTRACT FROM AUTHOR]

A novel method to prepare bulk Fe(Se0.5Te0.5) samples is presented, based on a melting process and a subsequent annealing treatment. With respect to the standard sintering technique, it produces much more homogeneous and denser samples, characterized by large and well interconnected grains. The resulting samples exhibit optimal critical temperature values, sharp resistive and magnetic transitions, large magnetic hysteresis loops and high upper critical fields. Interestingly, the global critical current density is much enhanced as compared to the values reported in the literature for bulk samples of the same 11 family, reaching about 103 A cm[?]2 at zero field at 4.2 K, as assessed by magnetic, transport and magneto-optical techniques. Even more importantly, its field dependence turns out to be very weak, such that at u0H = 7 T it is suppressed only by a factor [?]2. [ABSTRACT FROM AUTHOR]

We present a systematic characterization of Mg1[?]xLixB2 polycrystalline samples with nominal Li content x up to 0.30. We explore the effectiveness of the substitution and investigate its influence on superconducting and normal state properties. The structural analyses by neutron and x-ray diffraction indicate that, despite the lattice parameters remaining unchanged within the experimental accuracy, around 30% of the nominal Li content actually enters the structure. Also the transition temperature is only weakly affected by Li substitution, but its relationship with the residual resistivity and magnetoresistivity data is compatible with a picture where p bands are filled with holes and/or affected by disorder, as predicted by theory. We also measured the magnetic penetration depth l by an inductance technique. Data fits based on the standard Bardeen-Cooper-Schrieffer two-band model yield the zero-temperature limit of both l and superconducting gaps: we find that l(0) increases weakly and quickly saturates with increasing x, whereas Dp(0) and Ds(0) decrease with x. This analysis suggests that lithium substitution induces disorder mainly in the p band. Point contact spectroscopy results on samples obtained from the same batch are in full agreement with magnetic penetration depth data on the undoped sample, but give superconducting gaps almost insensitive to Li substitution, showing at most a small increase in Dp(0) that may be related to an inhomogeneous distribution of Li content. [ABSTRACT FROM AUTHOR]

The complex magnetic ordering of parent compounds of most unconventional superconductors is crucial for the understanding of high-temperature superconductivity (SC). Within this framework, we have performed temperature-dependent magnetotransport experiments on a single crystal of SmFeAsO, a parent compound of iron pnictide superconductors. We observe multiple features in the measured transport properties at temperatures below the antiferromagnetic (AFM) ordering of Sm, $T < {T_{{\text{NSm}}}}$ , which evolve with in-plane magnetic field, suggesting a rich variety of metamagnetic transitions never before observed in this compound. Considering that transport mainly involves Fe d orbitals at the Fermi level, these findings suggest that the features originate from magnetic transitions of the Fe moments sublattice, which in turn may be induced by magnetic transitions of the Sm moments sublattice via the interaction between Fe and Sm moments. We outline a possible scenario in which the Fe moments, strongly affected by the Sm ordering below T _NSm , reorder to an in-plane canted AFM structure, which is washed out by the application of an in-plane magnetic field up to 9 T. Our work shows that transport properties are a valuable tool for investigating magnetic ordering in iron pnictide parent compounds, where the interplay of magnetism and SC is believed to be the origin of high-temperature SC.

Copper-based chalcogenides have emerged as promising thermoelectric materials due to their high thermoelectric performance, tunable transport properties, earth abundance and low toxicity. We have presented an overview of experimental results and first-principal calculations investigating the thermoelectric properties of various polymorphs of Cu 2 SnS 3 (CTS), Cu 2 ZnSnS 4 (CZTS), and Cu 2 ZnSnSe 4 (CZTSe) synthesized by high-energy reactive mechanical alloying (ball milling). Of particular interest are the disordered polymorphs of these materials, which exhibit phonon-glass-electron-crystal behavior-a decoupling of electron and phonon transport properties. The interplay of cationic disorder and nanostructuring leads to ultra-low thermal conductivities while enhancing electronic transport. These beneficial transport properties are the consequence of a plethora of features, including trap states, anharmonicity, rattling, and conductive surface states, both topologically trivial and non-trivial. Based on experimental results and computational methods, this report aims to elucidate the details of the electronic and lattice transport properties, thereby confirming that the higher thermoelectric (TE) performance of disordered polymorphs is essentially due to their complex crystallographic structures. In addition, we have presented synchrotron X-ray diffraction (SR-XRD) measurements and ab initio molecular dynamics (AIMD) simulations of the root-mean-square displacement (RMSD) in these materials, confirming anharmonicity and bond inhomogeneity for disordered polymorphs.

The potential of Fe 2 TiSn full-Heusler compounds for thermoelectric applications has been suggested theoretically, but not yet proven experimentally, due to the difficulty in obtaining reproducible, homogeneous, phase-pure and defect-free samples. In this work, we studied Fe 2 TiSn 1- x Sb x polycrystals ( x from 0 to 0.6), fabricated by high-frequency melting and long-time high-temperature annealing. We obtained fairly good phase purity, a homogeneous microstructure, and good matrix stoichiometry. Although the intrinsic p-type transport behavior is dominant, n-type charge compensation by Sb-doping is demonstrated. Calculations of the formation energy of defects and electronic properties carried out using the density functional theory formalism reveal that charged iron vacancies V Fe 2- are the dominant defects responsible for the intrinsic p-type doping of Fe 2 TiSn under all types of (except Fe-rich) growing conditions. In addition, Sb substitutions at the Sn site give rise either to Sb Sn , Sb Sn 1+ , which are responsible for n-type doping and magnetism (Sb Sn ) or to magnetic Sb Sn 1- , which act as additional p-type dopants. Our experimental data highlight good thermoelectric properties close to room temperature, with Seebeck coefficients up to 56 μV/K in the x = 0.2 sample and power factors up to 4.8 × 10 -4 W m -1 K -2 in the x = 0.1 sample. Our calculations indicate the appearance of a pseudogap under Ti-rich conditions and a large Sb-doping level, possibly improving further the thermoelectric properties.

The development of simple, scalable, and cost-effective methods to prepare Van der Waals materials for thermoelectric applications is a timely research field, whose potential and possibilities are still largely unexplored. In this work, we present a systematic study of ink-jet printing and drop-casting deposition of 2H phase SnSe 2 and WSe 2 nanoflake assemblies, obtained by liquid phase exfoliation, and their characterization in terms of electronic and thermoelectric properties. The choice of optimal annealing temperature and time is crucial for preserving phase purity and stoichiometry and for removing dry residues of ink solvents at inter-flake boundaries, while maximizing the sintering of nanoflakes. An additional pressing is beneficial to improve nanoflake orientation and packing, thus enhancing electric conductivity. In nanoflake assemblies deposited by drop casting and pressed at 1 GPa, we obtained thermoelectric power factors at room temperature up to 2.2 × 10 -4 mW m -1 K -2 for SnSe 2 and up to 3.0 × 10 -4 mW m -1 K -2 for WSe 2 ., (© 2021 IOP Publishing Ltd.)

The process of developing superconducting materials for large scale applications is mainly oriented to optimize flux pinning and the current carrying capability. A powerful approach to investigate pinning properties is to combine high resolution imaging with transport measurements as a function of the magnetic field orientation, supported by a pinning modelling. We carry out Transmission Electron Microscopy, Electron Energy Loss Spectroscopy and critical current measurements in fields up to 16 T varying the angle between the field and c-axis of Fe(Se,Te) epitaxial thin films deposited on CaF 2 substrates. We find evidence of nanoscale domains with different Te:Se stoichiometry and/or rotated and tilted axes, as well as of lattice distortions and two-dimensional defects at the grain boundaries. These elongated domains are tens of nm in size along the in-plane axes. We establish a correlation between these observed microstructural features and the pinning properties, specifically strongly enhanced pinning for the magnetic field oriented in-plane and pinning emerging at higher fields for out-of-plane direction. These features can be accounted for within a model where pinning centers are local variations of the critical temperature and local variations of the mean free path, respectively. The identification of all these growth induced defects acting as effective pinning centers may provide useful information for the optimization of Fe(Se,Te) coated conductors., (© 2021. The Author(s).)

The purpose of this study was to assess validity, stability and sensitivity, of 4 spectral parameters-median frequency (F med ), mean frequency (F mean ), Dimitrov index (DI), and mean instant frequency (F mi )-in measuring localized muscle fatigue in swimming and to investigate their correlation with the variations of kinematic data and mechanical fatigue. Electrophysiological measures of muscle fatigue were obtained in real-time during a 100 m front crawl test at maximum speed in 15 experienced swimmers, using surface electromyography in six muscles employed in front crawl, while kinematic data of swimming was measured from video analysis. Mechanical fatigue was measured as the difference between muscle strength prior to and immediately after the 100 m front crawl in a dry-land multi-stage isometric contraction test. Statistically significant fatigue ( p < 0.0001) was found for all spectral parameters in all muscles. F med and F mean varied between 10 and 25%, DI between 50 and 150%, and F mi between 5 and 10%. Strong correlation (Pearson r ≥ 0.5) with mechanical fatigue was found for all spectral parameters except for F mi and it was strongest for F med and F mean . From our study, it turns out that F med and F mean are more valid and stable parameters to measure fatigue in swimming, while DI is more sensitive., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Puce, Pallecchi, Marinelli, Mori, Bove, Diotti, Ruggeri, Faelli, Cotellessa and Trompetto.)

Context: Kinesio Taping (KT) produces several clinical effects, including pain relief, edema absorption, and improved muscle performance. When applied in the insertion to origin mode, it is claimed to inhibit excessive muscle contractions., Objective: Investigate whether KT applied in the insertion to origin mode could reduce the exaggerated reflex contraction of spastic muscles., Design: Randomized crossover trial, with a restricted block randomization., Setting: Clinical laboratory and swimming pool., Patients: Seven para-swimmers., Intervention: KT, applied in inhibitory mode, to investigate its effect on knee extensor spasticity., Main Outcome Measures: Primary outcome is stretch reflex, as compared with clinical assessment of spasticity by Modified Ashworth Scale and self-perceived spasticity by numeric rating scale. Secondary outcomes were Medical Research Council for strength of knee extensor muscles and chronometric swimming performance in 100-m freestyle., Results: KT significantly decreased the amplitude of stretch reflex (P < .001), whereas the placebo treatment produced no significant effects. Scores of Medical Research Council for strength and Modified Ashworth Scale did not change after KT, whereas numeric rating scale scores for spasticity significantly decreased (P = .001). The swimming performance was significantly improved after KT treatment as compared with baseline (P < .01)., Conclusions: This exploratory study performed on para-athletes suggests that KT could reduce spasticity. This outcome has 3-fold implications for clinical, rehabilitation, and sport methods.

Spasticity is the velocity-dependent hypertonia frequently encountered in patients affected by Upper Motor Neuron Syndrome. It is due to a tonic stretch reflex, which is evoked in patients at rest. The aim of this study, performed using surface electromyography (EMG), was to investigate stretch reflex excitability in the hamstrings muscles of patients affected by progressive Multiple Sclerosis (MS) and to correlate EMG results with clinical findings. Thirty patients and 20 age-matched healthy controls were investigated. EMG activity was recorded from biceps femoris muscle with the patient at rest. To stretch hamstrings muscles, the patient's leg was manually moved from maximal flexion to maximal extension at 3 different velocities to investigate both phasic and tonic stretch reflex. Only 7 patients were affected by hypertonia of the hamstrings; 4 of them showed muscle contracture. A tonic stretch reflex was present in the vast majority of the recruited patients, whether they presented hypertonia of the hamstrings or not. Tonic stretch reflex is often present in the hamstrings muscles of progressive MS patients without producing increased muscle tone. This "ghost spasticity" is likely to be, for its intrinsic features, an important risk factor for the development of contractures in the hamstrings muscles., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Regular practice of sport activities yields psychophysical benefits for both the general population and persons affected by physical or intellectual impairments. Practicing competitive sport may add further value to these benefits. The objective of this observational cross-sectional study was to investigate the role of competitive sport practice in enhancing self-perceived psychophysical well-being of some select participants, using the Psychological General Well-Being Index and the Short Form-12 indices. We recruited at national events 100 young Italian competitive swimmers affected by physical or intellectual impairment. These respondents' results were compared with those of a control group of 100 Italian participants who did not practice competitive sport but who were also affected by physical or intellectual impairment, randomly selected from rehabilitation clinics and communities of young people with disabilities. Scores of psychological and emotional well-being were higher by 40% or more for the practitioners of competitive sport ( p  < .0001; Cohen's effect size d  ≥ 1.3). While our study's results suggest possible positive psychophysical benefits to competitive sport practice for young people affected by physical or intellectual impairment, longitudinal research is needed to be certain that our results are not due to self-selection into sports participation of those persons with disabilities who have a uniquely higher sense of well-being.

We study the electronic structure of the SmFeAsO 1-x F x alloy by means of first-principle calculations. We find that, contrary to common believe, F-doping does not change the charge balance between electrons and holes free-carriers in SmFeAsO 1-x F x . For energies within a narrow energy range accross [Formula: see text], the effect of F-doping on the band structure dispersion is tiny in both the paramagnetic and stripe antiferromagnetic phase. The charge balance between the conducting FeAs-layer and the SmO 1-x F x charge reservoir layer is not influenced by the compositional change. The additional charge carried by fluorine, with respect to the oxygen, is compensated by a change in the oxidation state of the Sm ion from 3+  to 2+. A comparison with the SmFe 1-x Co x AsO system shows that such charge compensation by the Sm ion is not shared by donors substituting at the Fe site.

Anisotropy of transport and magnetic properties of parent compounds of iron based superconductors is a key ingredient of superconductivity. In this work, we investigate in-plane and out-of-plane properties, namely thermal, electric, thermoelectric transport and magnetic susceptibility in a high quality BaFe 2 As 2 single crystal of the 122 parent compound, using a combined experimental and theoretical approach. Combining the ab initio calculation of the band structure and the measured in-plane and out-of-plane resistivity, we evaluate the scattering rates which turn out to be strongly anisotropic and determined by spin excitations in the antiferromagnetic state. The observed anisotropy of thermal conductivity is discussed in terms of anisotropy of sound velocities which we estimate to be [Formula: see text]. Remarkably, we find that thermal conductivity is characterized by a sizeable electronic contribution at low temperature, which is ascribed to the high purity of our crystal.

The goal of this work is providing a comprehensive interpretation framework for the wide and varied experimental phenomenology of the Seebeck effect in MgB 2 samples with different levels of doping in either π or σ bands and different levels of disorder, using a combined experimental and theoretical approach. We calculate the temperature dependent diffusive Seebeck coefficient S diff (T) with the Boltzmann equation resolved in relaxation time approximation, taking into account the scattering with phonons and impurities, the effect of renormalization and the effect doping in a rigid band approximation. We show that selective disorder has a sizeable effect on the S diff magnitude, as it tunes the relative contributions of σ and π bands. Disorder also affects the S diff temperature dependences, eventually yielding a linear S diff (T) behavior in the dirty limit. We also show that band filling has opposite effects on S, depending on which band dominates transport. In parallel, we carry out the Seebeck effect measurements on neutron-irradiated Mg 11 B 2 , and on two series of doped samples Mg 1-x Al x B 2 and Mg(B 1-x C x ) 2 . From comparison of calculated S diff (T) and experimental S(T) curves, we demonstrate that diffusive and phonon drag terms give comparable contributions in clean samples, but the phonon drag term is progressively suppressed with increasing disorder. In C and Al doped samples we observe very different experimental behaviors in terms of sign, magnitude and temperature dependence. Indeed, notwithstanding the similar electron doping introduced by both substitutions, C or Al doping yields disorder which mainly affects either σ or π bands, respectively. With the help of our theoretical approach, we are able to disentangle the various effects and prove that the Seebeck coefficient is a very sensitive probe of this kind of disorder.

Training methods for Paralympic swimmers must take into account different pathologies, competitions classes, athlete's individual circumstances and peculiar physical adaptation mechanisms, hence general guidelines cannot be found in literature. In this study we present a training program, implemented for the physical preparation of a top level Paralympic swimmer. The athlete under study, affected by infantile cerebral palsy within a clinical picture of a spastic tetraparesis, by the end of 2016 was holder of Italian, European, world and Paralympic titles in the 400-m freestyle competition, S6 class. The training macrocycle was structured in a 3-fold periodization (three mesocycles), in view of the preparation to three international competitions. The 4-month training mesocycles prior to each competition differed substantially in terms of mileage load, intensity and recovery times. The first mesocycle was characterized by a sizeable low-intensity mileage load, the second one was shifted to lower mileage load, carried out at middle-to-high intensity levels, the third one entailed increased effort intensity, counterbalanced by lower mileage load. In all cases, recovery times were balanced to obtain optimized performance through physical adaptation to training stimuli, keeping into account the physiopatological response. Tapering phases were adjusted to maximize performance at competition. As an assessment of the effectiveness of the training method, correspondence between chronometric and technical parameters in the three competitions and the respective mesocycle training programs was found. The results of the present study may support the development of training guidelines for athletes affected by upper motor neuron lesions., Competing Interests: CONFLICT OF INTEREST No potential conflict of interest relevant to this article was reported.

Background: We present the detailed protocol set up to investigate how agonistic sport affects the self-perceived psychological and emotional well-being of disabled young people., Methods: The study will be carried out on a number of subjects as large as 800-1200, using well-established indices that give a quantitative measure of such well-being, namely SF-12 and PGWBI. The related questionnaires will be administered to the participants to a forthcoming international event, the European Para-Youth Games, 9-15 October 2017, Liguria, Italy, as well as to a reference population of a similar number of subjects, made up of young disabled people that do not practice agonistic sport., Discussion: We expect that the outcomes of the study may strongly impact not only the socio-sanitary field but also society in general, as disabled people can be considered an extreme situation in the issue of balancing individual needs and environment to pursue psychological well-being., Trial Registration: ISRCTN14389453 (29 June 2017).

Advances in growth technology of oxide materials allow single atomic layer control of heterostructures. In particular delta doping, a key materials' engineering tool in today's semiconductor technology, is now also available for oxides. Here we show that a fully electric-field-tunable spin-polarized and superconducting quasi-2D electron system (q2DES) can be artificially created by inserting a few unit cells of delta doping EuTiO3 at the interface between LaAlO3 and SrTiO3 oxides. Spin polarization emerges below the ferromagnetic transition temperature of the EuTiO3 layer (TFM = 6-8 K) and is due to the exchange interaction between the magnetic moments of Eu-4f and of Ti-3d electrons. Moreover, in a large region of the phase diagram, superconductivity sets in from a ferromagnetic normal state. The occurrence of magnetic interactions, superconductivity and spin-orbit coupling in the same q2DES makes the LaAlO3/EuTiO3/SrTiO3 system an intriguing platform for the emergence of novel quantum phases in low-dimensional materials.

The goal of this work is to study the evolution of thermoelectric transport across the members of the Ruddlesden-Popper series iridates [Formula: see text], where a metal-insulator transition driven by bandwidth change occurs, from the strongly insulating Sr2IrO4 to the metallic non Fermi liquid behavior of SrIrO3. Sr2IrO4 ([Formula: see text]), Sr3Ir2O7 ([Formula: see text]) and SrIrO3 ([Formula: see text]) polycrystals are synthesized at high pressure and characterized by structural, magnetic, electric and thermoelectric transport analyses. We find a complex thermoelectric phenomenology in the three compounds. Thermal diffusion of charge carriers accounts for the Seebeck behavior of Sr2IrO4, whereas additional drag mechanisms come into play in determining the Seebeck temperature dependence of Sr3Ir2O7 and SrIrO3. These findings reveal a close relationship between magnetic, electronic and thermoelectric properties, strong coupling of charge carriers with phonons and spin fluctuations as well as the relevance of multiband description in these compounds.

We report the observation of spatially separated Kondo scattering and ferromagnetism in anatase Ta0.06Ti0.94O2 thin films as a function of thickness (10-200 nm). The Kondo behavior observed in thicker films is suppressed on decreasing thickness and vanishes below ~25 nm. In 200 nm film, transport data could be fitted to a renormalization group theory for Kondo scattering though the carrier density in this system is lower by two orders of magnitude, the magnetic entity concentration is larger by a similar magnitude and there is strong electronic correlation compared to a conventional system such as Cu with magnetic impurities. However, ferromagnetism is observed at all thicknesses with magnetic moment per unit thickness decreasing beyond 10 nm film thickness. The simultaneous presence of Kondo and ferromagnetism is explained by the spatial variation of defects from the interface to surface which results in a dominantly ferromagnetic region closer to substrate-film interface while the Kondo scattering is dominant near the surface and decreasing towards the interface. This material system enables us to study the effect of neighboring presence of two competing magnetic phenomena and the possibility for tuning them.

Understanding the nature of charge carriers at the LaAlO3/SrTiO3 interface is one of the major open issues in the full comprehension of the charge confinement phenomenon in oxide heterostructures. Here, we investigate thermopower to study the electronic structure in LaAlO3/SrTiO3 at low temperature as a function of gate field. In particular, under large negative gate voltage, corresponding to the strongly depleted charge density regime, thermopower displays high negative values of the order of 10(4)-10(5) μVK(-1), oscillating at regular intervals as a function of the gate voltage. The huge thermopower magnitude can be attributed to the phonon-drag contribution, while the oscillations map the progressive depletion and the Fermi level descent across a dense array of localized states lying at the bottom of the Ti 3d conduction band. This study provides direct evidence of a localized Anderson tail in the two-dimensional electron liquid at the LaAlO3/SrTiO3 interface.

Structural refinement, lattice micro-strain and spontaneous strain analyses have been carried out on selected members of the La(Fe1-xRux)AsO system using high-resolution neutron and synchrotron powder diffraction data. The obtained results indicate that the character of the tetragonal to orthorhombic structural transition changes from first order for x = 0.10, possibly to tricritical for x = 0.20, up to second order for x = 0.30; for x ≥ 0.40 symmetry breaking is suppressed, even though a notable increase of the lattice micro-strain develops at low temperature. By combining structural findings with previous muon spin rotation data, a phase diagram of the La(Fe1-xRux)AsO system has been drawn. Long-range ordered magnetism occurs within the orthorhombic phase (x ≤ 0.30), whereas short-range magnetism appears to be confined within the lattice strained region of the tetragonal phase up to x < 0.60. Direct comparison between the magnetic and structural properties indicates that the magnetic transition is always associated with structural symmetry breaking, although confined to a local scale at high Ru contents.

We explore the electronic, transport and thermoelectric properties of Fe 1+ y Se x Te 1- x compounds to clarify the mechanisms of superconductivity in Fe-based compounds. We carry out first-principles density functional theory (DFT) calculations of structural, electronic, magnetic and transport properties and measure resistivity, Hall resistance and Seebeck effect curves. All the transport properties exhibit signatures of the structural/magnetic transitions, such as discontinuities and sign changes of the Seebeck coefficient and of the Hall resistance. These features are reproduced by calculations provided that antiferromagnetic correlations are taken into account and experimental values of lattice constants are considered in DFT calculations. On the other hand, the temperature dependences of the transport properties can not be fully reproduced, and to improve the agreement between experiment and DFT calculations it is necessary to go beyond the constant relaxation time approximation and take into account correlation effects.

In this paper we show diverse methods for patterning transition metal oxide (TMO) thin films by Local Anodic Oxidation (LAO) using an Atomic Force Microscope (AFM). At first, direct lithography by current-controlled LAO of TMO thin films and selective wet etching is presented. For insulating films or those whose AFM patterns cannot be selectively removed by wet etching, fabrication of nanomasks is required; thus, the fabrication of Molybdenum and TMO nanomasks is reported. As a further development, we show the AFM fabrication of Mo/poly(methylmethacrylate) (PMMA) nanomasks through multistep processes combining LAO of Mo and dry etching of PMMA. Detailed discussions and comparisons between these methods are presented.