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Magnetic polar materials feature an astonishing range of physical properties, such as magnetoelectric coupling, chiral spin textures, and related new spin topology physics. This is primarily attributable to their lack of space inversion symmetry in conjunction with unpaired electrons, potentially facilitating an asymmetric Dzyaloshinskii-Moriya (DM) exchange interaction supported by spin-orbital and electron-lattice coupling. However, engineering the appropriate ensemble of coupled degrees of freedom necessary for enhanced DM exchange has remained elusive for polar magnets. Here, we study how spin and orbital components influence the capability of promoting the magnetic interaction by studying two magnetic polar materials, α-Cu(IO3)2 (2D) and Mn(IO3)2 (6S), and connecting their electronic and magnetic properties with their structures. The chemically controlled low-temperature synthesis of these complexes resulted in pure polycrystalline samples, providing a viable pathway to prepare bulk forms of transition-metal iodates. Rietveld refinements of the powder synchrotron X-ray diffraction data reveal that these materials exhibit different crystal structures but crystallize in the same polar and chiral P21 space group, giving rise to an electric polarization along the b-axis direction. The presence and absence of an evident phase transition to a possible topologically distinct state observed in α-Cu(IO3)2 and Mn(IO3)2, respectively, imply the important role of spin-orbit coupling. Neutron diffraction experiments reveal helpful insights into the magnetic ground state of these materials. While the long-wavelength incommensurability of α-Cu(IO3)2 is in harmony with sizable asymmetric DM interaction and low dimensionality of the electronic structure, the commensurate stripe AFM ground state of Mn(IO3)2 is attributed to negligible DM exchange and isotropic orbital overlapping. The work demonstrates connections between combined spin and orbital effects, magnetic coupling dimensionality, and DM exchange, providing a worthwhile approach for tuning asymmetric interaction, which promotes evolution of topologically distinct spin phases.

Bottom-up assembly of optically nonlinear and magnetically anisotropic lanthanide materials involving precisely placed spin carriers and optimized metal-ligand coordination offers a potential route to developing electronic architectures for coherent radiation generation and spin-based technologies, but the chemical design historically has been extremely hard to achieve. To address this, we developed a worthwhile avenue for creating new noncentrosymmetric chiral Ln

Magnetic skyrmions, which are topologically distinct magnetic spin textures, are gaining increased attention for their unique physical properties and potential applications in spintronic devices. Here we present a design strategy for skyrmion host candidates based on combinations of magnetic spin, asymmetric building units having stereo-active lone-pair electrons, and polar lattice symmetry. To demonstrate the viability of the proposed rational design principles, we successfully synthesized Fe(IO3)3 polycrystalline sample and single crystals by using a new simplified low-temperature pathway, which is experimentally feasible for extending materials growth of transition metal iodates. Single crystal X-ray and powder synchrotron X-ray diffraction measurements demonstrated that Fe(IO3)3 crystallizes in the polar chiral hexagonal lattice with space group P63. The combined structural features of the macroscopic electric polarization along the c axis stemming from the coalignment of the stereo-active lone-pairs of the IO3 trigonal pyramid and the magnetic Fe3+cation residing on the three-fold rotation axis were selected to promote asymmetric exchange coupling. We find evidence of a predicted skyrmion phase at 14 K to 16 K and 2.5 T to 3.2 T driven by Dzyaloshinskii Moriya (DM) interaction, a conclusion supported by the appreciable DM exchange and the zero-field spiral antiferromagnetic ground state of Fe(IO3)3 deduced from neutron diffraction experiments. The associated magnetic modulation wavelength of the putative skyrmions is expected to be short, approximately 18 nm, comparable to the period of the DM-driven incommensurate order. This work links stereo-active lone-pair electron effects to enhanced DM interaction, demonstrating a new approach for chemical guidelines in the search for skyrmionic states of matter.

We report a successful synthesis of a ternary AlB2-type intermetallic compound. The phase purity was obtained by fine-tuning the Pd : Ge ratio out of the idealized 1 : 3. Attempts to synthesize an Er analogue were not successful. We discuss the instability of the Er analogue based on the atomic size ratio and also suggest that the increased stability of Ho2Pd1+xGe3−x in the Pd-rich range likely stems from a combination of atomic size ratio, electronic, and entropic factors. The new Ho2Pd1.3Ge2.7 compound is found to exhibit cluster glass behavior with a freezing temperature of T ≈ 2.3 K.

Superconductivity is reported in an endohedral aluminide compound, RuAl6, with Tc = 1.21 K. The normalized heat capacity jump at Tc, ΔC/γTc = 1.58, confirms bulk superconductivity. The Ginzburg–Lan...

We present the crystallographic analysis, superconducting characterization and theoretical modeling of LiBi, that contains the lightest and the heaviest nonradioactive metal. The compound crystallizes in a tetragonal (CuAu-type) crystal structure with Bi square nets separated by Li planes (parameters a = 3.3636(1) Å and c = 4.2459(2) Å, c/a = 1.26). Superconducting state was studied in detail by magnetic susceptibility and heat capacity measurements. The results reveal that LiBi is a moderately coupled type-I superconductor (λe-p = 0.66) with Tc = 2.48 K and a thermodynamic critical field Hc(0) = 157 Oe. Theoretical studies show that bismuth square net is responsible for superconductivity in this compound, but the coupling between the Li planes and Bi planes makes a significant contribution to the superconductivity.

Magnetic polar materials feature an astonishing range of physical properties, such as magnetoelectric coupling, chiral spin textures, and related new spin topology physics. This is primarily attributable to their lack of space inversion symmetry in conjunction with unpaired electrons, potentially facilitating an asymmetric Dzyaloshinskii-Moriya (DM) exchange interaction supported by spin-orbital and electron-lattice coupling. However, engineering the appropriate ensemble of coupled degrees of freedom necessary for enhanced DM exchange has remained elusive for polar magnets. Here, we study how spin and orbital components influence the capability of promoting the magnetic interaction by studying two magnetic polar materials, α-Cu(IO

Polycrystalline LiGa2Ir has been prepared by a solid state reaction method. A Rietveld refinement of powder x-ray diffraction data confirms a previously reported Heusler-type crystal structure (space group Fm-3m, No. 225) with lattice parameter a = 6.0322(1) Å. The normal and superconducting state properties were studied by magnetic susceptibility, heat capacity, and electrical resistivity techniques. A bulk superconductivity with Tc = 2.94 K was confirmed by detailed heat capacity studies. The measurements indicate that LiGa2Ir is a weak-coupling type-II superconductor ($${\uplambda }$$ λ e–p = 0.57, $${\Delta }$$ Δ C/$${\upgamma }$$ γ Tc = 1.4). Electronic structure, lattice dynamics, and the electron–phonon interaction are studied from first principles calculations. Ir and two Ga atoms equally contribute to the Fermi surface with a minor contribution from Li. The phonon spectrum contains separated high frequency Li modes, which are seen clearly as an Einstein-like contribution in the specific heat. The calculated electron–phonon coupling constant $${\uplambda }$$ λ e–p = 0.68 confirms the electron–phonon mechanism for the superconductivity. LiGa2Ir and recently reported isoelectronic LiGa2Rh are the only two known representatives of the Heusler superconductors with the valence electron count VEC = 16.

While exploring novel magnetic semiconductors, the new phase Cr0.65Al1.35Se3 was discovered and characterized by both structural and physical properties. Cr0.65Al1.35Se3 was found to crystallize into orthorhombic CrGeTe3-type structure with space group Pnma (no. 62). Vacancies and mixed occupancies were tested, and the results show that one of the 4c sites accommodates a mixture of Cr and Al atoms, while the other 4c site is fully occupied by Al atoms. Unique structural features include a T-shaped channel network created from the edge-sharing Cr/Al@Se6 and Al@Se4 polyhedra and a zipper effect of the puckered Se atoms inside the columnar channels. The round peak observed in the temperature-dependent magnetic susceptibility (χg) plot at ∼8(1) K corresponds to the antiferromagnetic-type transition in Cr0.65Al1.35Se3. However, the positive θCW indicates an additional ferromagnetic interaction, which is highly likely due to the complex magnetic structure arising from the mixed Cr/Al occupancies on the 4c site. Electrical resistivity measurements confirm that Cr0.65Al1.35Se3 is a semimetal with a positive magnetoresistance. Here we present the characterization and determination of the crystal structure and physical properties for this new material.

Three new salt inclusion compounds (Cs X)Cu5O2(PO4)2 ( X = Cl, Br, I), phosphate analogues of the kagome mineral averievite, are reported. Their crystal structures are composed of trigonal networks of corner-sharing OCu4 anion-centered tetrahedra, forming capped-kagome planes, which can also be regarded as two-dimensional slices along the [111] direction of a pyrochlore lattice. Magnetization and heat capacity measurements reveal strong geometric frustration of this network and complex magnetic behavior. X-ray and neutron diffraction studies show that all three compounds undergo a trigonal-to-monoclinic phase transition upon cooling, with a first-order phase transition seen in CsBr and CsI analogues. Along with the previously reported (CsCl)Cu5O2(VO4)2, these three new compounds belong to a large family of OCu4-based networks, which are a playground for studying frustrated quantum magnetism.

We report a successful synthesis of a ternary AlB

We report the synthesis and physical properties of a full Heusler compound, $\mathrm{Mg}{\mathrm{Pd}}_{2}\mathrm{Sb}$, which we found to show superconductivity below ${T}_{c}=2.2\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. $\mathrm{Mg}{\mathrm{Pd}}_{2}\mathrm{Sb}$ was obtained by a two-step solid-state reaction method and its purity and cubic crystal structure [$Fm\text{\ensuremath{-}}3m, a=6.4523(1)\phantom{\rule{0.16em}{0ex}}\AA{}$] were confirmed by powder x-ray diffraction. Normal and superconducting states were studied by electrical resistivity, magnetic susceptibility, and heat capacity measurements. The results show that $\mathrm{Mg}{\mathrm{Pd}}_{2}\mathrm{Sb}$ is a type-II, weak coupling superconductor (${\ensuremath{\lambda}}_{e\text{\ensuremath{-}}p}=0.53$). The observed pressure dependence of ${T}_{c}$ ($\mathrm{\ensuremath{\Delta}}{T}_{c}/p\ensuremath{\approx}--0.23\phantom{\rule{0.16em}{0ex}}\mathrm{K}/\mathrm{GPa}$) is one of the strongest reported for a superconducting Heusler compound. The electronic structure, phonons, and electron-phonon coupling in $\mathrm{Mg}{\mathrm{Pd}}_{2}\mathrm{Sb}$ were theoretically investigated. The obtained results are in agreement with the experiment, confirming the electron-phonon coupling mechanism of superconductivity. We compare the superconducting parameters to those of all reported Heusler-type superconductors.

The $\mathrm{spin}\text{\ensuremath{-}}\frac{1}{2}$ Heisenberg antiferromagnetic chain is ideal for realizing one of the simplest gapless quantum spin liquids (QSLs), supporting a many-body ground state whose elementary excitations are fractional fermionic excitations called spinons. Here we report the discovery of such a one-dimensional (1D) QSL in $\mathrm{C}{\mathrm{s}}_{4}\mathrm{CuS}{\mathrm{b}}_{2}\mathrm{C}{\mathrm{l}}_{12}$. Compared to previously reported $S=\frac{1}{2}$ 1D chains, this material possesses a wider temperature range over which the QSL state is stabilized. We identify spinon excitations extending at $Tg0.8\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, with a large $T$-linear contribution to the specific heat, $\ensuremath{\gamma}=31.5(2)\phantom{\rule{0.16em}{0ex}}\mathrm{mJ}\phantom{\rule{0.16em}{0ex}}\mathrm{mo}{\mathrm{l}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}2}$, which contribute itinerantly to thermal transport up to temperatures as high as $T=35\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. At $T=0.7\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, we find a second-order phase transition that is unchanged by a ${\ensuremath{\mu}}_{0}H=5\phantom{\rule{0.16em}{0ex}}\mathrm{T}$ magnetic field. $\mathrm{C}{\mathrm{s}}_{4}\mathrm{CuS}{\mathrm{b}}_{2}\mathrm{C}{\mathrm{l}}_{12}$ reveals new phenomenology deep in the 1D QSL regime, supporting a gapped QSL phase over a wide temperature range compared to many other experimental realizations.

New, monometallic nanoparticles (MNPs) decorated surface and rare earth (RE) ions doped lattice of perovskite-type (KTaO 3 )/pyrochlore-type (K 2 Ta 2 O 6 ) photocatalysts were successfully prepared by facile hydrothermal incorporation of RE ions into KTaO 3 /K 2 Ta 2 O 6 lattices followed by photodeposition of MNPs. The impact of noble metal type (MNPs = Au, Pt, Rh) and rare earth dopant type (RE = Er, Pr) on the physicochemical properties correlated with photoactivity of MNPs/RE-KTaO 3 and MNPs/RE-K 2 Ta 2 O 6 has been examined. All as-prepared photocatalysts were systematically characterized by UV–vis diffuse reflectance spectroscopy, photoluminescence emission spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, fast Fourier transform, powder X-ray diffraction, and X-ray photoelectron spectroscopy. The crystal structure was presented using VESTA software. Photocatalytic activity of samples under visible light irradiation was determined by pollutant decomposition, while UV–vis induced activity was estimated by H 2 generation efficiency. The experimental results suggested a synergistic effect between MNPs and RE-ions-modified KTaO 3 /K 2 Ta 2 O 6 , which resulted in greatly improved photocatalytic performance compared with that of pristine KTaO 3 /K 2 Ta 2 O 6 . Inclusion of RE ions into KTaO 3 /K 2 Ta 2 O 6 lattices probably leads to formation of RE4 f states below the conduction band levels to electron transition by lower photon excitation energy, while photoreduction of MNPs on the RE-KTaO 3 /RE-K 2 Ta 2 O 6 surface causes localized surface plasmon resonance and activates surface by adsorption for both O 2 and H 2 O molecules. The highest visible-light-induced photoactivity was observed for the Au/Er-KTaO 3 sample (16.48%) in phenol solution degradation and for the Pt/Pr-K 2 Ta 2 O 6 photocatalyst (36.13%) in gaseous toluene removal, respectively. Active species-trapping tests indicate that O 2 − radicals are meaningfully involved in phenol oxidation under visible light irradiation. The largest amount of H 2 evaluation was observed for the Pt/Pr-K 2 Ta 2 O 6 sample (93.16 µmol/min) under UV–vis irradiation, which also showed a relatively good lifetime in recycling. The present study describes noble- and rare-earth-metal-modified KTaO 3 /K 2 Ta 2 O 6 as an advanced material in photocatalysis.

Novel mono- and bimetallic nanoparticles (MNPs and BNPs) decorated surface of perovskite-type KTaO3 photocatalysts were successfully synthesized by hydrothermal reaction of KTaO3 followed by photodeposition of MNPs/BNPs. The effect of noble metal type (MNPs = Au, Ag, Pt, Pd, Rh, Ru or BNPs = Au/Pt, Ag/Pd, Rh/Ru), amount of metal precursor (0.5, 1.0, 1.5 or 2.0 wt%) as well as photoreduction method (simultaneous (both) or subsequent (seq) deposition of two metals) on the physicochemical and photocatalytic properties of MNPs- and BNPs-KTaO3 have been investigated. All as-prepared photocatalysts were subsequently characterized by UV–Vis diffuse reflectance spectroscopy (DRS), Brunauer-Emmett-Teller (BET) specific surface area and pore size distribution measurement, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (PXRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) emission spectroscopy. The crystal structure was performed using visualization for electronic and structural analysis (VESTA). The photocatalytic activity under Vis light irradiation was estimated in phenol degradation in aqueous phase and toluene removal in gas phase, while under UV–Vis light irradiation was measured amount of H2 generation from formic acid solution. The absorption properties of O2 and H2O molecules on KTaO3(1 0 0) surface supported by Au or Au/Pt NPs was also investigated using density-functional theory (DFT). The experimental results show that, both MNPs-KTaO3 and BNPs-KTaO3 exhibit greatly enhanced pollutant decomposition efficiency under Vis light irradiation and highly improved H2 production under UV–Vis light irradiation compared with pristine KTaO3. MNPs deposition on KTaO3 surface effects by disperse metal particle size ranging from 11 nm (Ru NPs) to 112 nm (Au NPs). Simultaneous addition of Au/Pt precursors results in formation of agglomerated larger metal nanoparticles (50–100 nm) on KTaO3 surface than subsequent deposition of Au/Pt with composition of concentrated smaller metal nanoparticles (>50 nm) on KTaO3 surface. The 0.5 Au/1.5 Pt-KTaO3_both and 2.0 Rh-KTaO3 reveal the highest Vis-induced activity among prepared samples in aqueous phase (14.75% of phenol decomposition after 90 min of irradiation) and gas phase (41.98% of toluene removal after 60 min of irradiation), respectively. The theoretical calculations confirmed that adsorption energy of O2 and H2O molecules was increased after loading of Au or Au/Pt NPs on KTaO3(1 0 0) surface. Control tests with scavengers show that O2 − radical is significantly involved in phenol oxidation under Vis light irradiation, which proposed mechanism is based on direct electron transfer from MNPs/BNPs to conduction band of KTaO3. The highest amount of H2 evaluation is obtained also by 0.5 Au/1.5 Pt-KTaO3_both after 240 min of UV–Vis light irradiation (76.53 µmol/min), which is eleven times higher than for pristine KTaO3 (6.69 µmol/min). Moreover, the most photocatalytic samples for each model reaction present good repeatability and stability after subsequent three cycles. Summarized, MNPs- and BNPs-KTaO3 are promising material in advanced applications of photocatalysis.

Novel rare earth-doped K2Ta2O6 (RE-K2Ta2O6) photocatalysts were successfully synthesized by one-step hydrothermal method. The effect of dopant type (RE = Y, Yb, Ho, Pr, Er) and amount of rare earth precursor (2, 4, 8 and 10 mol%) on the physicochemical and photocatalytic properties of RE-K2Ta2O6 have been investigated. All as-prepared materials were subsequently characterized by UV–vis diffuse reflectance spectroscopy (DRS), Brunauer-Emmett-Teller (BET) specific surface area measurement, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, mass magnetic susceptometry and photoluminescence (PL) emission spectroscopy. The photocatalytic activity under UV–vis light irradiation was estimated in phenol degradation in aqueous phase, toluene removal in gas phase and H2 generation from formic acid solution. The experimental results show that, novel RE-K2Ta2O6 exhibits greatly improved degradation efficiency under UV–vis light irradiation compared with pristine K2Ta2O6. The Er-K2Ta2O6 and Pr-K2Ta2O6, obtained by introducing of 2 mol% of RE ions during synthesis, reveal the highest photocatalytic activity among prepared samples in aqueous phase (33% of phenol decomposition after 90 min of irradiation) and gas phase (45% of toluene removal after 60 min of irradiation), respectively. Moreover, both photocatalysts present good stability after subsequent three cycles. The active species trapping test shows that OH and O2 − radicals are significantly involved in phenol oxidation under UV–vis light irradiation. The amount of H2 evolution increases with increasing addition of Er dopant into K2Ta2O6 lattice. The highest H2 production is obtained for 10 mol% Er-K2Ta2O6 after 240 min of UV–vis light irradiation (15.40 μmol/min). Enhanced photoactivity performance can be attributed to incorporation of RE ions at K+ lattice site in RE-K2Ta2O6, probably leading to formation of new RE 4f states below the conduction band of K2Ta2O6 structure. To investigate the localization of RE ions in K2Ta2O6 structure, the band structure and partial density of the states (PDOS) have been investigated. Computer simulations were performed using plane-wave based Vienna ab-initio simulation package (VASP) with the generalized gradient approximation (GGA) by Perdew-Burke-Ernzerhof (PBE). Moreover, inclusion of RE ions in K2Ta2O6 causes predominance pyrochlore phase formation over perovskite in regular cubic structure. Summarized, RE-doped K2Ta2O6 is promising material in photocatalytic degradation of organic pollutants and H2 generation processes. Our work may provide valuable information for rare earth doping semiconductor with improved photocatalytic performance.

In this study, we report a novel method of BaZrO3 and SrZrO3 surface modification by two different types of quantum dots (QDs, Cu2O and Bi2O3), which improved the photocatalytic performance of the obtained materials under UV-Vis light irradiation. Pristine BaZrO3 and SrZrO3 were prepared by the hydrothermal method. The deposition of Cu2O- and Bi2O3-QDs was carried out by chemical reduction. The morphology of the nanoparticles was estimated based on microscopic analysis (SEM, TEM). The perovskite structure and phase composition of polycrystals were confirmed by X-ray powder diffraction analysis (XRD). The elemental surface composition and the chemical character of detected elements were identified by X-ray photoelectron spectroscopy (XPS). The absorption ability and luminescence properties of nanocomposites were investigated by UV–Vis diffuse-reflectance spectroscopy (DRS UV-Vis) and luminescence spectroscopy. The influence of Cu2O/Bi2O3-QDs modification on the photocatalytic activity of BaZrO3 and SrZrO3 was evaluated by the phenol photodegradation process in the liquid phase under UV-Vis and toluene degradation in the gas phase under Vis irradiation. The highest photoactivity under UV-Vis light was observed for BaZrO3/1% Cu2O/33% Bi2O3 and SrZrO3/1% Cu2O/33% Bi2O3 samples. Research also demonstrated that single-type QD deposition (Cu2O or Bi2O3) on the zirconate surface decreases the photoactivity in comparison with pristine zirconates. The mechanism of photocatalytic activity of the obtained nanocomposites was investigated by the formation of hydroxyl radicals under UV-Vis irradiation in the presence of terephthalic acid.

Facile and environmentally benign one-step titanium anodization method for TiO 2 nanotubes (NTs) formation in a presence of ionic liquids (ILs) was proposed. Influence of the IL structure and its content in ethylene glycol electrolyte on morphology, surface properties and photoactivity of the TiO 2 NTs was investigated. Possible interactions between IL and TiO 2 NTs as well as the mechanism of NTs formation during anodic oxidation process were proposed. The outer diameter, wall thickness, and length of the IL-NTs were found to be proportionally related with increasing length of the hydrocarbon chain in the imidazolium cation of the IL (from 2 to 8), IL content, anodization potential and water content up to 10 vol.%. Moreover, for the first time, the effect of the IL’s structure on the UV–vis and Vis light-induced photoactivity of the IL-TiO 2 NTs was presented, and the active species ( OH and O 2 − radicals) involved in the photocatalytic reaction of phenol degradation were determined. The sample that exhibited the highest photoactivity under Vis irradiation (0.63 μmol dm −3 min −1 ) and greatest amounts of generated OH was TiO 2 NTs prepared at anodization potential 90 V in the electrolyte containing 0.1 mol of 1-octyl-3-methylimidazolium tetrafluoroborate [OMIM][BF 4 ] (represented by F − content) and 10 vol.% of water. Phenol degradation rate remained at level about 1.50 and 0.42 μmol dm −3 min −1 after 60 min of UV–vis and Vis irradiation after four cycles in the presence of [OMIM][BF 4 ] and thus obtained IL-NTs exhibited photostability. The reaction proceeds under mild reaction conditions, is step economical and provides one-dimensional nanostructures that meet the specifications for use in diverse photocatalytic applications.

A heterojunction with excellent visible light response and stability based on titanium dioxide nanotubes (TiO2 NTs), bismuth sulfide quantum dots (Bi2S3 QDs), and platinum nanoparticles (Pt NPs) is proposed. Both Pt NPs (3.0 ± 0.2 nm) and Bi2S3 QDs (3.50 ± 0.20 nm) are well distributed on the (i) top parts, (ii) inner walls, and (iii) outer walls of the TiO2 NTs. Visible-light-induced photoreaction was initialized by excitation of narrow band gap Bi2S3 QDs, followed by electron injection to the conduction band of TiO2, while Pt NPs acted as electron traps, enhacing O2–• generation. Phenol in the aqueous phase and toluene in the gas phase were efficiently degraded over Bi2S3–Pt NTs, even for wavelengths longer than 455 and 465 nm, respectively, while no degradation of model compounds was observed over pristine TiO2 NTs under the same irradiation conditions. Photocatalytic tests of phenol degradation in the presence of scavengers revealed that superoxide radicals were responsible for the visible-light degra...

Polycrystalline samples of HoT2Al20 (T = Ti, V, Cr) intermetallics were synthesized using a step-wise arc-melting technique. All three compounds adopt the CeCr2Al20-type crystal structure with Ho atoms positioned inside oversized icosahedral cages formed by Al atoms. The structure of HoV2Al20 compound is reported. The materials properties were studied by means of electrical resistivity, magnetic susceptibility, and specific heat measurements. All three compounds show a Curie-Weiss paramagnetic behavior down to 1.95 K. Specific heat measurements show the presence of electronic Schottky anomaly resulting from crystal-field splitting of Ho3+ energy levels in the three compounds, while in HoTi2Al20 and HoV2Al20 a second anomaly was observed, resulting from the presence of low-energy Einstein phonon mode.

A series of Er-, Yb-, Ho-, Tb-, Gd-, Pr-TiO 2 nanotubes (RE-NTs) was prepared via an electrochemical method. The as-prepared photocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis absorption, scanning electron microscopy (SEM) and luminescent spectroscopy. The experiments demonstrated that toluene in the gas phase was successfully degraded under visible light (LEDs λ max = 465 nm) using RE-NTs. In the presence of the most active sample (Ho-NTs), the photodegradation of toluene reached 30% after 60 min of vis irradiation. To investigate the localization of RE in the TiO 2 structure, computer simulations were performed using the plane-wave-based Vienna ab-initio simulation package (VASP) implementing spin-polarized density-functional theory (DFT) and the generalized gradient approximation (GGA). It is proposed that during the electrochemical process, TiO 2 systems with new Ho-f states below the conduction band of TiO 2 is formed. The photocatalytic activity under Vis irradiation is attributable not to OH but to other forms of reactive oxygen species (O 2 − , HO 2 , H 2 O 2 ).

Well-organized TiO2 nanotube arrays were fabricated via one-step anodization process. The as-prepared TiO2 nanotubes were characterized by X-ray powder diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS) and scanning electron microscopy (SEM). Photocatalytic activity of obtained photocatalyst was studied in reaction of toluene degradation in the gas phase using low powered and low cost light-emitting diodes (UV LEDs) as an irradiation source. The effect of irradiation intensity and initial pollutant concentration on gas phase photoactivity of TiO2 nanotubes was analyzed. Obtained TiO2 nanotubes were smooth and vertically oriented with a length of about 1.7 ± 0.05 μm. The inner diameter and the wall thickness were 65 ± 2 nm and 6 ± 0.4 nm, respectively. The results showed that the initial toluene degradation rate increased (from 0.0062 up to 0.0567 μmol/min) with raising initial toluene concentration (50–400 ppm), while too high dose of irradiation (about 50 mW/cm2) reduced photocatalytic toluene degradation rate. The best stability of TiO2 nanotubes in three subsequent irradiation cycles was observed for irradiation intensity of 38 mW/cm2. Moreover, it was found that photocatalytic toluene degradation over TiO2 nanotubes showed first order kinetic behavior.

The development of a photocatalyst with remarkable activity to degrade pollutants in aqueous and gas phase requires visible light-responsive stable materials, easily organized in the form of a thin layer (to exclude the highly expensive separation step). In this work, we present a one-step strategy for synthesizing material in the form of a self-organized TiO2/Ag2O nanotube (NT) array interlaced with silver nanoparticles (as in a cake with raisins) that exhibited photoactivity significantly enhanced compared to that of pristine TiO2 NTs under both ultraviolet (UV) and visible (vis) irradiation. An NT array composed of a mixture of TiO2 and Ag2O and spiked with Ag nanoparticles was formed via the anodization of a Ti–Ag alloy in a one-step reaction. Silver NPs have been formed during the in situ generation of Ag ions and were (i) embedded in the NT walls, (ii) stuck on the external NT walls, and (iii) placed inside the NTs. The enhancement of photocatalytic efficiency can be ascribed to the existence of an ...

While exploring novel magnetic semiconductors, the new phase Cr

In this work, we present our discovery and characterization of a new kagome prototype structure, ${\mathrm{KV}}_{3}{\mathrm{Sb}}_{5}$. We also present the discovery of the isostructural compounds ${\mathrm{RbV}}_{3}{\mathrm{Sb}}_{5}$ and ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$. All materials exhibit a structurally perfect two-dimensional kagome net of vanadium. Density-functional theory calculations indicate that the materials are metallic, with the Fermi level in close proximity to several Dirac points. Powder and single-crystal syntheses are presented, with postsynthetic treatments shown to deintercalate potassium from single crystals of ${\mathrm{KV}}_{3}{\mathrm{Sb}}_{5}$. Considering the proximity to Dirac points, deintercalation provides a convenient means to tune the Fermi level. Magnetization measurements indicate that ${\mathrm{KV}}_{3}{\mathrm{Sb}}_{5}$ exhibits behavior consistent with a the Curie-Weiss model at high temperatures, although the effective moment is low $(0.22{\ensuremath{\mu}}_{\text{B}}$ per vanadium ion). An anomaly is observed in both magnetization and heat capacity measurements at 80 K, below which the moment is largely quenched. Elastic neutron scattering measurements find no obvious evidence of long-range or short-range magnetic ordering below 80 K. The possibility of an orbital-ordering event is considered. Single-crystal resistivity measurements show the effect of deintercalation on the electron transport and allow estimation of the Kadowaki-Woods ratio in ${\mathrm{KV}}_{3}{\mathrm{Sb}}_{5}$. We find that $A/{\ensuremath{\gamma}}^{2}\ensuremath{\sim}61\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{Ohm}$ cm ${\mathrm{mol}}_{\text{FU}}^{2}\phantom{\rule{4pt}{0ex}}{\mathrm{K}}^{2}\phantom{\rule{4pt}{0ex}}{\mathrm{J}}^{\ensuremath{-}2}$, suggesting that correlated electron transport may be possible. ${\mathrm{KV}}_{3}{\mathrm{Sb}}_{5}$ and its cogeners ${\mathrm{RbV}}_{3}{\mathrm{Sb}}_{5}$ and ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$ represent a new family of kagome metals, and our results demonstrate that they deserve further study as potential model systems.

In the present study we report a successful synthesis of the new intermetallic compound Nd2PtGe3 by an arc-melting method. The powder X-ray diffraction analysis indicates that this compound crystallizes in an disordered variant of the AlB2-type structure (space group P6/mmm, no. 191) with lattice parameters a = 4.2455 A and c = 4. 1933 A. The compound exhibits a cluster-glass transition below Tf = 2.9 K, characterized through ac and dc magnetic susceptibility and heat capacity measurements.

Following the predictions of total energy calculations, a tetragonal SrMn2P2 phase is proposed and successfully formed under high pressure. At ambient pressure, SrMn2P2 adopts the primitive trigonal La2O3 structure type (space group P3[combining macron]m1). However, the results of total energy calculations indicate that SrMn2P2 should be more stable in the tetragonal ThCr2Si2 structure type (space group I4/mmm) than in its known trigonal structure, thus motivating our synthetic experiments. Guided by these calculations, a new tetragonal polymorph of SrMn2P2 was found under the relatively mild conditions of 5 GPa applied pressure at a temperature of 900 °C through the transformation of the ambient pressure trigonal form. The new polymorph has the body centered tetragonal ThCr2Si2 structure type, as predicted. The electronic structure calculations indicate the likelihood of antiferromagnetic, semiconducting properties for the high pressure SrMn2P2 phase.

The crystallographic, electronic transport and thermal properties of Ca 2 PdGe 3 and Ca 2 PtGe 3 are reported. The compounds crystalize in an ordered variant of the AlB 2 crystal structure, in space group P 6/mmm , with the lattice parameters a = 8.4876(4) A/8.4503(5) A and c = 4.1911(3) A/4.2302(3) A for Ca 2 PdGe 3 and Ca 2 PtGe 3 , respectively. The resistivity data exhibit metallic behavior with residual-resistivity-ratios (RRR) of 13 for Ca 2 PdGe 3 and 6.5 for Ca 2 PtGe 3 . No superconducting transition is observed down to 0.4 K. Specific heat studies reveal similar values of the Debye temperatures and Sommerfeld coefficients: Θ D = 298 K, γ = 4.1 mJ mol − 1 K − 2 and Θ D = 305 K, γ = 3.2 mJ mol − 1 K − 2 for Ca 2 PdGe 3 and Ca 2 PtGe 3 , respectively. The low value of γ is in agreement with the electronic structure calculations.

Nitrogen doped TiO 2 nanotube arrays were prepared by anodizing Ti foils in an organic electrolyte containing specified amounts of urea as nitrogen precursor. The photocatalytic activity of the samples was evaluated by analyzing the degradation kinetics of phenol in water. The influence of tubes’ length, tubes’ surface morphology and amount of nitrogen in the TiO 2 lattice on hydroxyl radical formation efficiency, photocatalytic activity and stability in four cycles was investigated. It was found that the photocatalytic activity as well as the charge carrier recombination rate depends on nitrogen concentration and the process parameters. 3.5 μm-long nanotubes containing 0.34 at.% of nitrogen seems to be favorable in phenol degradation and OH radicals generation under visible light. Comparison of XPS and photocatalytic activity test results shows decrease in phenol degradation efficiency with increasing amount of carbon contaminants on photocatalysts’ surface.

La 3 Co and La 3 Ni are reported superconductors with transition temperatures of 4.5 and 6 K, respectively. Here, we reinvestigate the physical properties of these two intermetallic compounds with magnetic susceptibility χ, specific heat C p and electrical resistivity ρ measurements down to 1.9 K. Although bulk superconductivity is confirmed in La 3 Co, as observed previously, only a trace of it is found in La 3 Ni, indicating that the superconductivity in La 3 Ni originates from an impurity phase. Superconducting state parameters for La 3 Co, including lower and upper critical fields and the superconducting gap, are estimated. Results of the theoretical calculations of the electronic structure for both materials are also presented, and comparison of the Fermi level location in La 3 Co versus La 3 Ni explains its larger superconducting T c . A major discrepancy between band structure calculations and the experimentally measured Sommerfeld coefficient is found. The measured electronic density of states is about 2.5 times larger than the theoretical value for La 3 Co. This effect cannot be explained by the electron-phonon interaction alone. Renormalization of γ, as well as an ∼T 2 behavior of the resistivity, suggests the presence of spin fluctuations in both systems.

Single crystals of SrCo2Al and BaCo2Al9 were grown using a self-flux method. A LeBail analysis of the powder X-ray diffraction patterns show that both compounds crystallize in a hexagonal (P6/mmm) crystal structure with lattice parameters: a ​= ​7.8995(1) A, c ​= ​3.9159(1) A for SrCo2Al9, and a ​= ​7.9162(2) A, c ​= ​3.9702(1) A for BaCo2Al9 aluminide. The low temperature analysis of the heat capacity measurements give a Sommerfeld coefficient γ ​= ​4.99(6) mJ mol−1 K−2 for SrCo2Al9 and almost twice larger γ ​= ​7.94(9) mJ mol−1 K−2 for BaCo2Al9. Resistivity measurements show metallic-like behavior, with reasonably large residual resistivity ratio RRR ​= ​6 and 10 for SrCo2Al9 and BaCo2Al9, respectively. Neither heat capacity nor resistivity measurements reveal any phase transition down to 1.8 ​K.

A series of single semiconductors and their nanocomposites combination (such as KTaO 3 + CdSe + SrTiO 3 ; KTaO 3 + CdS + WO 3 ; KTaO 3 + CdS + MoS 2 ) were prepared using hydrothermal route. Photocatalytic activity of as-prepared nanocomposites was estimated by photocatalytic degradation of toluene in the gas phase using light-emitting diodes (LEDs, 375 nm) in four subsequent cycles. The nanocomposites were characterized by scanning electron microscopy (SEM), X-ray powder diffraction analysis (XRD), UV–vis diffuse-reflectance spectroscopy (DRS) and BET surface area measurements. It was observed that hierarchical 3D structures caused an increase of the photocatalytic activity in gas phase.

The structure, optical and electrical properties of manganese borosilicate glasses of the composition xMnO–(80 − x)SiO2–20B2O3 (x = 40, 50, and 60 mol%) were investigated. The dependence of the glass structure on its composition was discussed and related to electrical properties. A separation of two amorphous phases was observed. It was suggested that one phase is MnO-rich and the other is SiO2-rich. It was found that the conductivity of MnO-rich phase is much higher than the conductivity of the other phase. The analysis of the valence states of manganese suggest that the transition metal ions are mainly present at second oxidation state. Magnetic susceptibility measurements show antiferromagnetic interactions in samples.

Novel rGO–KTaO3 composites with various graphene content were successfully synthesized using a facile solvothermal method which allowed both the reduction of graphene oxide and loading of KTaO3 nanocubes on the graphene sheets. The as-prepared photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET) specific surface area, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), UV-Vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) emission spectroscopy. The obtained rGO–KTaO3 composites showed greatly improved photocatalytic performance for degradation of phenol under visible light irradiation (λ > 420 nm) over pristine KTaO3 which could be related to the photosensitizer role of graphene in the rGO–KTaO3 composites as well as the formation of p–n heterojunctions between KTaO3 nanocubes and rGO sheets. The highest photocatalytic activity in phenol degradation reaction was observed for rGO–KTaO3 hybrid with 30 wt% graphene. The enhanced photoactivity of this composite could be attributed to the synergistic effect of several factors such as: small crystallite size, extended absorption range in the visible spectrum and intimate contact between graphene and KTaO3 cubes.

In this article, the authors investigate the interplay between the Peierls instability and magnetism in members of the $R$NiC${}_{2}$ family, where $R$=Nd, Pr, Ce. Transport, magnetic, specific heat, and galvanomagnetic properties are studied. In NdNiC${}_{2}$, the charge density wave state is partially suppressed by an antiferromagnetic transition. The application of a strong enough magnetic field induces a ferromagnetic transition, accompanied by further destruction of the charge density wave and by a metastable lattice transformation. PrNiC${}_{2}$ shows the opposite behavior in that, although the Peierls instability is initially weakened by the Zeeman splitting of the conduction bands, the magnetic anomaly restores and even enhances the nesting conditions.

Following the predictions of total energy calculations, a tetragonal SrMn