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The competition between Ruderman-Kittel-Kasuya-Yosida (RKKY), crystal electric field (CEF), and Kondo energy scales has recently emerged at the heart of complex magnetism in several Ce- or Yb-based intermetallics. Hard axis magnetic order has been observed in a handful of these compounds, independent of the crystal symmetry, size of the ordered moment, or the relative scale of the Kondo and magnetic ordering temperatures. This raises the question of the role of each energy scale in driving the ground state properties. In focusing on a single class of compounds, the rhombohedral R${\mathrm{Rh}}_{3}{\mathrm{Si}}_{7}$, we compare the anisotropy and magnetic ground states in members of this series with only RKKY interactions (R = Gd), or RKKY and CEF effects (R = Tb-Tm), with the behavior of the R = Yb compound, where all three energy scales (RKKY, CEF, Kondo) are at play. Moreover, we extend the comparison to two other isostructural Kondo systems ${\mathrm{YbIr}}_{3}{\mathrm{Si}}_{7}$ and ${\mathrm{YbIr}}_{3}{\mathrm{Ge}}_{7}$, where hard axis magnetic order is also observed. The non-Kondo compounds R${\mathrm{Rh}}_{3}{\mathrm{Si}}_{7}$ (R = Tb-Tm) lack the complexity of magnetic order along the hard CEF axis, pointing to the dominant role of the Kondo effect in driving this magnetic order. However, the CEF-RKKY competition is still responsible for complex magnetic ground states, and it appears that the electronic and magnetic degrees of freedom are entangled in all magnetic members of this series of compounds.

Metal-to-insulator transitions (MIT) can be driven by a number of different mechanisms, each resulting in a different type of insulator—Change in chemical potential can induce a transition from a metal to a band insulator; strong correlations can drive a metal into a Mott insulator with an energy gap; an Anderson transition, on the other hand, due to disorder leads to a localized insulator without a gap in the spectrum. Here, we report the discovery of an alternative route for MIT driven by the creation of a network of narrow channels. Transport data on Pt substituted for Ti in 1T-TiSe2 shows a dramatic increase of resistivity by five orders of magnitude for few % of Pt substitution, with a power-law dependence of the temperature-dependent resistivity ρ(T). Our scanning tunneling microscopy data show that Pt induces an irregular network of nanometer-thick domain walls (DWs) of charge density wave (CDW) order, which pull charge carriers out of the bulk and into the DWs. While the CDW domains are gapped, the charges confined to the narrow DWs interact strongly, with pseudogap-like suppression in the local density of states, even when they were weakly interacting in the bulk, and scatter at the DW network interconnects thereby generating the highly resistive state. Angle-resolved photoemission spectroscopy spectra exhibit pseudogap behavior corroborating the spatial coexistence of gapped domains and narrow domain walls with excess charge carriers.

Triangular lattice of rare-earth ions with interacting effective spin-$1/2$ local moments is an ideal platform to explore the physics of quantum spin liquids (QSLs) in the presence of strong spin-orbit coupling, crystal electric fields, and geometrical frustration. The Yb delafossites, NaYbCh$_2$ (Ch=O, S, Se) with Yb ions forming a perfect triangular lattice, have been suggested to be candidates for QSLs. Previous thermodynamics, nuclear magnetic resonance, and muon spin rotation measurements on NaYbCh$_2$ have supported the suggestion of the QSL ground states. The key signature of a QSL, the spin excitation continuum, arising from the spin quantum number fractionalization, has not been observed. Here we perform both elastic and inelastic neutron scattering measurements as well as detailed thermodynamic measurements on high-quality single-crystalline NaYbSe$_2$ samples to confirm the absence of long-range magnetic order down to 40 mK, and further reveal a clear signature of magnetic excitation continuum extending from 0.1 to 2.5 meV. The comparison between the structure of the magnetic excitation spectra and the theoretical expectation from the spinon continuum suggests that the ground state of NaYbSe$_2$ is a QSL with a spinon Fermi surface., Comment: 18 pages, 6 figures

We excited terahertz magnons in Er*Yi_*FeO3 as a function of temperature, magnetic field, and yttrium composition (x), providing insight into the role of cooperative Er3+-Fe3+ exchange interactions in the low-temperature phase transition.

The micro-electromechanical systems (MEMS) process and packaging with poly-dimethylsiloxane (PDMS) polymer materials are important technologies in semiconductor industries. In this study, we propose using the L9 orthogonal array to determine the optimal parameters for an optical fiber sensor packaged with PDMS. According to analysis of variance results, the optimal parameters are as follows: a grating with a diameter of 60 μm, a period of 650 μm, and a length of 2.5 cm, as well as a photoresist structure with a width of 2 mm. The results of a large-the-best (LTB) analysis indicated that the expected sensitivity value of a sensor with those parameters would be around 0.0345 dB⁄μe. After testing and verification, the sensitivity results indicated a mean sensitivity of 0.0339 dB⁄μe, with the deviation in sensitivity being less than 0.14%.

In this paper, two transparent thin-film transistors (TFTs) with distinct channel designs were fabricated. The first was a single-channel TFT (SC-TFT) with a typical 50-nm-thick amorphous indium–gallium–zinc oxide (a-IGZO) layer, and the second was a sandwich composite-channel TFT (CC-TFT) comprising three layers of 10-/30-/10-nm-thick Ti-doped GaZnO (GTZO)/a-IGZO/GTZO. In the CC-TFT, the bottom GTZO thin film in the composite channel exhibited a highly smooth surface, serving as a buffer template for superior IGZO channel layer thin-film growth. The top GTZO thin film had a high carrier concentration and served as both a carrier supplement and passivation layer for reducing the adsorption of moisture and oxygen molecules. The studies of material quality indicated that the CC-TFT exhibited improved a-IGZO thin-film quality; relative to the SC-TFT, the oxygen vacancy concentration of the composite structure was reduced from 25.1% to 18.2%. The CC-TFT demonstrated a high level of device performance, exhibiting an excellent field-effect mobility of 14.1 cm2/ $\text{V}\,\cdot \, \text{s}$ , subthreshold swing of 0.33 V/decade, off current of $2.92 \times 10^{-12}$ A, threshold voltage of 1.7 V, and on–off current ratio of $3.95 \times 10^{7}$ . Stable device operation with nearly unaltered device characteristics was observed following a bias-stress test.

We report the discovery of ${\mathrm{Ce}}_{3}{\mathrm{Ir}}_{4}{\mathrm{Ge}}_{13}$, a Remeika phase with a complex array of structural, electronic, and magnetic properties. Our single crystal x-ray diffraction measurements show that ${\mathrm{Ce}}_{3}{\mathrm{Ir}}_{4}{\mathrm{Ge}}_{13}$ forms in the tetragonally distorted $I{4}_{1}/amd$ space group, which has three distinct rare earth sites. The electrical resistivity is almost temperature independent over three decades in temperature, from 0.4 K to 400 K, while the Hall coefficient measurements are consistent with a low-carrier semimetal. Magnetic susceptibility measurements reveal an effective moment, ${\ensuremath{\mu}}_{\mathrm{eff}}^{\mathrm{exp}}=1.87{\ensuremath{\mu}}_{B}/\mathrm{Ce}$, that falls significantly short of the expected value for ${\mathrm{Ce}}^{3+}$, suggesting that two of the rare earth sites are occupied by magnetic ${\mathrm{Ce}}^{3+}$ while the third is occupied by nonmagnetic ${\mathrm{Ce}}^{4+}$. Upon cooling, ${\mathrm{Ce}}_{3}{\mathrm{Ir}}_{4}{\mathrm{Ge}}_{13}$ first enters a short range magnetically ordered state below ${T}_{\text{SRO}}=10\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, marked by a deviation from Curie-Weiss behavior in susceptibility and a broad field-independent heat capacity anomaly. At lower temperatures, we observe a second, sharper peak in the heat capacity at ${T}^{*}=1.7\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, concurrent with a splitting of the field-cooled and zero-field-cooled susceptibilities. A small resistivity drop at ${T}^{*}$ suggests a loss of spin disorder scattering consistent with a magnetic ordering or spin freezing transition. ${\mathrm{Ce}}_{3}{\mathrm{Ir}}_{4}{\mathrm{Ge}}_{13}$ is therefore a rare example of an inhomogeneous mixed valence compound with a complex array of thermodynamic and transport properties.

Single crystals of ${\mathrm{Sr}}_{2}{\mathrm{Mn}}_{3}{\mathrm{As}}_{2}{\mathrm{O}}_{2}$ have been grown for the first time, for which we show a possible layer-selective Mott insulator behavior. This compound stands out as a hybrid structure of ${\mathrm{MnO}}_{2}$ and MnAs layers, analogously to the active ${\mathrm{CuO}}_{2}$ and FeAs layers, respectively, in the cuprate and iron-based high-temperature superconductors. Electrical transport, neutron diffraction measurements, together with density functional theory calculations on ${\mathrm{Sr}}_{2}{\mathrm{Mn}}_{3}{\mathrm{As}}_{2}{\mathrm{O}}_{2}$ single crystals converge toward a picture of independent magnetic order at ${T}_{1}\ensuremath{\sim}79$ K and ${T}_{2}\ensuremath{\sim}360$ K for the two Mn sublattices, with insulating behavior at odds with the metallic behavior predicted by calculations. Furthermore, our inelastic neutron-scattering studies of spin-wave dispersions for the Mn(1) sublattice reveal an effective magnetic exchange coupling of $SJ\ensuremath{\sim}3.7$ meV. This is much smaller than those for the Mn(2) sublattice.

Dilute impurities and growth conditions can drastically affect the transport properties of TiSe$_2$, especially below the charge density wave transition. In this paper, we discuss the effects of cooling rate, annealing time and annealing temperature on the transport properties of TiSe$_2$: slow cooling of polycrystalline TiSe$_2$ post-synthesis drastically increases the low temperature resistivity, which is in contrast to the metallic behavior of single-crystalline TiSe$_2$ due to charge doping from the residual iodine transport agent. A logarithmic increase of resistivity upon cooling and negative magnetoresistance with a sharp cusp around zero field are observed for the first time for the polycrystalline TiSe$_2$ samples, pointing to weak-localization effects due to low dimensionality. Annealing at low temperatures has a similar, but less drastic effect. Furthermore, rapid quenching of the polycrystalline samples from high temperatures freezes in disorder, leading to a decrease in the low temperature resistivity., Comment: 8 pages, 6 figures

EuGa4 hosts a magnetic Eu2+ sublattice surrounded by a network of covalently-bound Ga atoms with the BaAl4 structure type (space group I4/ m m m ). In this study, we present the synthesis and characterization of three new single crystal substitutional series Eu A x 1 − x Ga4 with A ​= ​Ca, Sr, or La. X-ray diffraction and resistivity measurements show that Ca substitution induced a structural phase transition from the tetragonal crystal structure at high temperatures to the monoclinic crystal structure (CaGa4 type, space group C2/m) at low temperatures and suppressed the antiferromagnetic ordering temperature to 8.8 ​K for x ​= ​0.45. Comparatively, La or Sr substitution maintained the tetragonal crystal structure and suppressed the antiferromagnetic ordering temperatures to 6.7 ​K and 1.6 ​K for (A, x) = (La, 0.37) and (Sr, 0.91), respectively. In addition to suppressing the magnetic order, magnetization and specific heat measurements indicate the onset of anisotropic metamagnetic transitions in (La, 0.18), (La, 0.37), and (Sr, 0.63), along with an incommensurate-to-commensurate magnetic transition in (Sr, 0.38). By comparing these effects of doping EuGa4, we show how size, disorder, and charge determine the structure-physical property relations in EuGa4.

The solid solution $\mathrm{Eu}{({\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Al}}_{x})}_{4}$ was grown in single crystal form to reveal a rich variety of crystallographic, magnetic, and electronic properties that differ from the isostructural end compounds ${\mathrm{EuGa}}_{4}$ and ${\mathrm{EuAl}}_{4}$, despite the similar covalent radii and electronic configurations of Ga and Al. Here we report the onset of magnetic spin reorientation and metamagnetic transitions for $x=0--1$ evidenced by magnetization and temperature-dependent specific heat measurements. ${T}_{\mathrm{N}}$ changes nonmonotonously with $x$, and it reaches a maximum around 20 K for $x=0.50$, where the $a$ lattice parameter also shows an extreme (minimum) value. Anomalies in the temperature-dependent resistivity consistent with charge density wave behavior exist only for $x=0.50$ and 1. Density functional theory calculations show increased polarization between the Ga-Al covalent bonds in the $x=0.50$ structure compared to the end compounds, such that crystallographic order and chemical pressure are proposed as the causes of the charge density wave behavior.

The magnetic and transport properties of bulk doped manganite, La0.5−yYySr0.5MnO3 have been studied as a function of (Y) yttrium doping, y, for 0 ⩽ y ⩽ 0.25. In the absence of the yttrium this is a well studied half-doped manganite which is a metallic ferromagnet. With successive doping of Y the system undergoes a transformation from rhombohedral (space group R 3 ¯ - C ) to orthorhombically (space group Pnma) distorted perovskite structure, due to the large distortions caused by the yttrium; this is seen directly from the softening of the Mn–O stretching mode (around 600 cm−1) as a function of Y3+ doping which has relatively lower ionic radius compared to La3+ and Sr2+. These distortions make this series of compounds particularly interesting. The magnetization obtained in zero field cooled (ZFC) and field cooled (FC) studies show dramatic changes as the value of y is raised above 0.05. This is accompanied by a transition from the metallic and into a semiconducting state as is seen from the studies of the electrical resistivity. The magnetic behavior is further investigated by a study of the hysteresis loops, frequency dependent susceptibility and studies of the magnetic relaxation. The results are understood in terms of the average size of the cation on the A site, 〈rA〉, and the variance, σ2 (=∑yi2ri2 − 〈rA〉2). The value of the variance, σ2, increases rapidly with doping, y, induces weakening of the long range ferromagnetic ordering, exhibiting a stepwise variation of magnetization (metamagnetic like). Based on the present results a magnetic phase diagram has been drawn demonstrating different magnetic phase sequences with the variation of σ2.

We report the growth of thin films of ternary metal chalcogenide Ag 3 SbS 3 . The growth involves two steps: (1) Ag 3 SbS 3 nanoparticles were synthesized using the hydrothermal method; (2) a post-annealing process transformed the Ag 3 SbS 3 nanoparticles into Ag 3 SbS 3 films. The best Ag 3 SbS 3 nanoparticles were obtained with the hydrothermal reaction temperature of 140 °C for 12 h. The formation of Ag 3 SbS 3 films is sensitive to the annealing temperature and the best films were produced at 440 °C. The XRD pattern reveals the Ag 3 SbS 3 single phase. The prepared Ag 3 SbS 3 film has a smooth, uniform surface with a medium particle size of ~200 nm. Optical absorption reveals an energy gap of 1.8 eV and a large absorption coefficient of 2.1×10 5 cm −1 at λ =400 nm. The large optical absorption suggests that Ag 3 SbS 3 films could be a potential solar cell material. Compared to the laser technique used formally, the present growth method is simpler, lower cost and able to produce high-quality Ag 3 SbS 3 films.

The microscopic mechanism governing the zero-resistance flow of current in some iron-based, high-temperature superconducting materials is not well understood up to now. A central issue concerning the investigation of these materials is their superconducting gap symmetry and structure. Here we present a combined study of low-temperature specific heat and scanning tunnelling microscopy measurements on single crystalline FeSe. The results reveal the existence of at least two superconducting gaps which can be represented by a phenomenological two-band model. The analysis of the specific heat suggests significant anisotropy in the gap magnitude with deep gap minima. The tunneling spectra display an overall "U"-shaped gap close to the Fermi level away as well as on top of twin boundaries. These results are compatible with the anisotropic nodeless models describing superconductivity in FeSe., 8 pages, 5 figures

We investigated several FeSe single crystals grown by two different methods by utilizing experimental techniques namely, resistivity, magnetoresistance, specific heat, scanning tunneling microscopy, and spectroscopy. The residual resistivity ratio (RRR) shows systematic differences between samples grown by chemical vapor transport and flux vapor transport, indicating variance in the amount of scattering centers. Although the superconducting transition temperature $T_c$ is not directly related to RRR, our study evidences subtle differences in the features of an incipient ordering mode related to a depletion of density of states at the Fermi level. For instance, the onset temperature of anisotropic spin-fluctuations at $T^* \approx 75$ K, and the temperature of the opening-up of a partial gap in the density of states at $T^{**} \approx 30$ K are not discernible in the samples with lower RRR. Further, we show that the functional dependence of the electronic specific heat below 2 K, which allows to determine the nodal features as well as the small superconducting gap, differs significantly in crystals grown by these two different methods. Our investigation suggests that some of the controversies about the driving mechanism for the superconducting gap or its structure and symmetry is related to minute differences in the crystals arising due to the growth techniques used and the total amount of scattering centers present in the sample., Comment: 10 pages, 9 figures

The relationship between the oxygen pressure, porosity, adhesion, and ion beam-assisted deposition (IAD) conditions for WO 3 electrochromic films prepared using an electron-beam (E-beam) system was investigated. The adhesion of thin films on the substrate by sole E-beam system is very weak. The best method is proposed to obtain good adhesion and better porosity by combining the E-beam evaporation, and the microstructure and coloration efficiency were determined using a field emission scanning electron microscope (SEM) and a spectrometer, respectively. Notably, the effect of the oxygen pressure on the coloration efficiency and porosity of Ta 2 O 5 /WO 3 films was found to be different. The optimal average transmittance of the electrochromic film in the bleached state was 11%, and in the colored state was 68%, when a Ta 2 O 5 thin film was deposited in oxygen at a pressure at 9 × 10 -4 torr using IAD, and a WO 3 thin film was deposited at an oxygen pressure of 7.5 × 10 -5 torr. The studied results are useful for the design of more efficient photoelectrochemical devices employing evaporated WO 3 films.

We adopted sputtering techniques to produce Si thin films on IF (interstitial free) steel sheets in this study to obtain diffusivity of O and interdiffusion coefficients of Si and Fe in sputtered Si film. The microstructure of the coating system was analyzed by using XRD (X-ray diffractometry) and Raman spectroscopy. The compositional variations and the phase transformation within the diffusion zone at the end of diffusion annealing were inspected by employing GDOS (glow discharge optical spectrometry) and XPS (X-ray photoelectron spectroscopy). The diffusivities of Fe and Si for the Si-Fe diffusion couple calculated based on the Boltzmann-Matano method and the depth profiles from GDOS were found to vary from 2.40×10−15 to 4.24×10−14 cm2/s and 5.77×10−15 to 6.59×10−14 cm2/s, respectively. The diffusivity of O in the Si thin film, 2.19×10−14 cm2/s, was however obtained by employing Grube method. Low diffusivities of O and Fe within the Si film are the reason why sputtered Si film is suitable to serve as an...

Mn(OH)2/multi-walled carbon nanotube (MWCNT) composite thin films were obtained by spray coating on flexible indium tin oxide/polyethylene terephthalate substrate. The precursors for thin film deposition were prepared by completely mixing MWCNTs and KMnO4 in deionized water. The morphological characteristics of the films were examined by field emission scanning electronic microscopy and transmission electron microscopy. Phase evolution of the thin films was characterized by X-ray diffraction and X-ray photoelectron spectroscopy. As a result of the deposition process, Mn(OH)2 did not only cover the surface of MWCNTs uniformly but also embed in MWCNTs. The capacitive properties of the thin films were investigated by electrochemical measurements and the capacitance increased as the weight ratio of KMnO4/MWCNTs increased up to 1.6. The highest specific capacitance obtained at a scan rate of 20 mV s− 1 was 297.5 F/g for the composite thin film with the weight ratio of KMnO4/MWCNTs of 1.2.

A novel method using induction heating equipment was employed to investigate the thermal fatigue behaviors of two hot-work steels, JIS SKD61 and modified JIS SKD61, vacuum hardened treated to 45 HRC. Selected specimens, austenitized at 1298K for 25min, gas quenched to room temperature and tempered at 873K, were salt bath nitrocarburized at 843K for 80min and low pressure nitrided at 813K for 6h, respectively. Microstructure, microhardness, X-ray diffraction and thermal fatigue tests were conducted. The results show that the thermal fatigue properties of the 898K tempered specimen were better than those of other treated specimens. The reason is that the hardened processes would give high tensile strength, which improved the tool material thermal fatigue resistance. The thermal fatigue properties of modified JIS SKD61 specimen, including mean crack length and crack distribution density, were better than those of JIS SKD61 specimen. Low pressure nitriding treatment with a homogeneous nitrided layer could better maintain thermal fatigue resistance than the nitrocarburized steel.

This study proposes the notched long-period fiber grating (NLPFG) temperature sensor fabricated by inductive couple plasma (ICP) etching. The experimental results show that the largest sensitivity of the NLPFG sensor is 0.107 nm/°C. Therefore, the NLPFG temperature sensor possesses superior sensitivity.

In this experiment, we use the opaque mirror stainless steel as the substrate to investigate decorative color variations after insertion of the Na+ ion in the film and prescribe the combination coating film with reversible and excellent coating characteristics. In manufacturing of the coating film, reactive gas pass through the metal tungsten target and form the amorphous tungsten oxide thin film on stainless steel and the various colors, such as green and pink color, on the mirror stainless by adjusting the process parameters. The coating film device then immerse in sodium bicarbonate aqueous solution and induce cyclic potential of -2V～+2V. Base color of stainless steel produce the color change reaction by inserting Na+ in the film. Experimental observations show that the green base color will transform to pink then blue and the pink base color transform to green then blue.

This research compares the difference in determining the austenite amount in SKD 11 tool steel using the micrographic method as opposed to the X-ray diffraction method. Calculating the amount of retained austenite in tool steel using X-ray diffraction analysis requires first taking off the primary carbide content. By etching the SKD11 specimen using Beraha’s CdS reagent, the retained austenite, martensite and carbide are shown as white, red and blue regions in the microstructure, respectively. With quantitative metallography, the retained austenite can be distinguished as separate micro-constituents and properly counted. However, the calculated values are lower than those acquired from the X-ray diffraction. It is more accurate to evaluate the amount of retained austenite with carbide by X-ray diffraction analysis.

The corrosion behavior of the nitrocarburized JIS SKD61 and DH31S hot work steels has been investigated. The as received JIS SKD61 and DH31S steel was quenched and tempered to obtain the tempered martensitic microstructure. The nitrocarburizing treatment was conducted in a 570°C salt bath for 40, 80, and 120 minutes, respectively. Treated specimens were characterized by means of microstructural analysis, microhardness measurements, X-ray diffraction analysis, glow discharge spectrometer analysis and electrochemical tests in a 3.5wt% NaCl aerated solution. The thickness of compound layer of nitrocarburized specimens was about 1-3μm, and the microhardness is in the range between 790 – 820 HV0.05. The compound layer of the nitrided specimen was consisted of ε-phase (Fe2-3N) and the γ’-phase (Fe4N). The highest corrosion potential (Ecorr) in this study reached to -0.3 V for NC-S80 and NC-H80 specimen, it’s about 1.5 times higher than that of ferrite substrate. There is no evident difference on corrosion current density (Icorr) with prolonging nitrocarburizing treatment for both steels. Nevertheless, the corrosion properties were improved by nitrocarburizing process.

The fragile nature of itinerant magnetism can be exploited using non-thermal parameters to study quantum criticality. The recently discovered quantum critical point (QCP) in the Sc-doped (hole-like doping) itinerant antiferromagnet TiAu (Ti$_{1-x}$Sc$_{x}$Au) raised questions about the effects of the crystal and electronic structures on the overall magnetic behavior. In this study, doping with V (electron-like doping) in Ti$_{1-x}$V$_{x}$Au introduces chemical disorder which suppresses antiferromagnetic order from $T_{\rm N} =$ 36~K for $x = 0$ down to 10 K for $x =$ 0.15, whereupon a solubility limit is reached. Signatures of non-Fermi-liquid behavior are observed in transport and specific heat measurements similar to Ti$_{1-x}$Sc$_{x}$Au, even though Ti$_{1-x}$V$_{x}$Au is far from a QCP for the accessible compositions $x \leq 0.15$.

Photocatalytic activity of titania with poly(ethylene glycol) (PEG) in the sample films made under different operating conditions was investigated by kinetic analysis of photodegradation tests. The sample films, composed of PEG and nano-TiO 2 particles, were prepared by sol–gel processing and then treated thermally under an atmosphere of wet and dry air at different temperatures. After the thermal treatment, photocatalytic activities of the films were evaluated by a UV-exposure test. Results showed that the photoactivity was enhanced by processing in an atmosphere of wet air at 100 °C. Moreover, the presence of poly(ethylene glycol), and the change in surface morphology in the sample films were verified to be the most influential and significant factors to affect the photoactivitic activity.

The magnetic and transport properties of bulk doped manganite, La0.5−yYySr0.5MnO3 have been studied as a function of yttrium doping, y, for 0 ≤ y ≤ 0.25. In the absence of the yttrium this is a well studied half-doped manganite which is a metallic ferromagnet. The end members of this system (with y = 0 and 0.25) are found to be structurally different (rhombohedral and orthorhombic, respectively) due to the large distortions caused by the yttrium. These distortions make this series of compounds particularly interesting. The magnetization obtained in zero field cooled (ZFC) and field cooled (FC) studies show dramatic changes as the value of y is raised above 0.05. The magnetic behavior is further investigated by a study of the hysteresis loops, frequency dependent susceptibility and studies of the magnetic relaxation. The results are understood in terms of the average size of the cation on the A site, , and the variance, σ2 (= ∑yi2ri2 - 2). The value of the variance, σ2, increases rapidly with dopin...

Electrical transport (90–300 K) and magnetic (5–375 K) properties of the La0.67Ca0.33MnO3 + x% V2O5 (x = 0, 2, 5, 15 and 30) type magnetic–nonmagnetic composite system show appreciable grain boundary contribution. These composites, except for the one with x = 30%, show metal–insulator transitions at T = Tp which decrease with increasing V2O5 concentration. The high temperature (T > Tp) semiconducting part of the resistivity (ρ) data follow a small polaron hopping conduction mechanism. The magnetoresistance (MR) in this system increases with increasing V2O5 content, showing a maximum value (25% at 93 K and field H = 1.15 T) for the sample with x = 15%. Spin polarization is considered to be responsible for such an increase of MR. Neither thermoelectric power (between 90 and 300 K) nor magnetization data indicate any noticeable change of the Curie temperature (TC) with change of x, suggesting that V2O5 remains at the grain boundary. The complex impedance (Z*) of the composite system, measured over a frequency range of 0.01 kHz–13 MHz, at 300 K shows strong frequency dependence and the impedance plane plots (Z'–Z'') are semicircular for different V2O5 content. An equivalent resistor–capacitor circuit (Rg (Rgb Cgb)) has been proposed to explain the impedance results in this composite system.

Mesoporous TiO 2 thin films were prepared by hydrothermal-oxidation of titanium metal thin films, which were obtained by DC magnetron sputtering technique. Gold nanoparticles, which were prepared by reduction of HAuCl 4 , were embedded into the holes of the mesoporous TiO 2 films by capillary method followed by annealing in air up to 400 °C. The size of pore of TiO 2 films is about 100 nm and that of Au nanoparticles is about 10 nm in average. The morphology of the films was analyzed by field emission scanning electron microscope (FE-SEM) and scanning probe microscopes (SPMs). Subsequently, the photocatalytic performances of the obtained nanosystems in the decomposition of methylene blue solution are discussed. The obtained results show that the dispersion of Au nanoparticles on the mesoporous TiO2 matrix will help enhancing the photocatalytic activity with respect to pure TiO 2 under visible light irradiation.

To investigate the occurrence of superconductivity in the geometrically frustrated system, the V and Mn doping effects on the structure, electrical resistivity and superconducting transition temperature Tc of LiTi2O4 are studied, where LiTi2O4 is the only Spinel oxide superconductor and its isostructural compounds LiV2O4 and LiMn2O4 are claimed to be a 3d heavy fermion and a high-voltage electrolyte, respectively. The rapid increase of resistivity is observed in the Mn-doping samples, but the Tc is not correspondingly suppressed from magnetization measurement. However, it shows different behavior in the V-doping samples. The significance of V and Mn doping effects on LiTi2O4 and the electronic role of 3d transition metals in Spinel oxides are discussed. r 2006 Published by Elsevier B.V.

CP-Ti and Ti-153 were adopted in this study to observe their electrochemical behavior in serving as the cathode for photovoltaic hydrogen production. The designed cyclic hydrogenation-solution heat treating processes were performed to increase the hydrogen uptake for both alloys. The results are as follows. (1) Both arsenic trioxide and thiourea showed hydrogenation promotive effect on CP-Ti, while thiourea was an inhibitor for Ti-153 under the applied conditions. (2) Arsenic trioxide showed hydrogenation promotive effect on both Ti-153 and CP-Ti in this study. (3) Ti-153 demonstrated superiority to CP-Ti when serves as the cathode for photovoltaic hydrogen production. The hydrogen mass payload for Ti-153 is 68 times larger than that for CP-Ti.

The specific heat of CeAu2Ge2 single crystals grown from Au-Ge (AGF) or Sn flux (SF) was measured at temperatures T between 1.8 and 200 K. Two magnetic transitions are observed in the zero-field specific heat at 12.1 and 14.5 K in the AGF sample, while only a single sharp transition at 9.2 K is seen in the SF sample, confirming our recent susceptibility results [Fritsch et al., Phys. Rev. B 84, 104446 (2011)]. We observe several field-induced transitions in the magnetoresistance of the AGF sample measured at 1.6 and 2.3 K in accordance with the B-T phase diagram constructed from isothermal magnetization curves M(B). In addition, we have measured M(B) under hydrostatic pressure P up to 10.5 kbar. The Neel temperature TN increases linearly with P at a small rate of 0.049 K/kbar, which suggests that, if TN(P ) is attributed to a pure volume effect, this compound is close to the maximum transition temperature of the Doniach diagram. The transition fields BM between the field-induced phases increase linearly with P as well. The comparable Gruneisen parameters of TN and BM indicate that the energy scale depending on the sample’s volume is given by the antiferromagnetic correlations and not by the Kondo effect. We discuss possible reasons for the different magnetic behavior of AGF and SF samples.

dc and ac magnetization measurements were performed on single-crystal Cu2OSeO3 under magnetic field (H) and hydrostatic pressure (P) conditions. Increasing H shifts the ferrimagnetic transition observed at T-C similar to 60 K to a higher-temperature region. Moreover, the T-C increases linearly and magnetization is enhanced with P. Features of the ladder in the M-vs-H curve or the peak in the dM/dH-vs-H curve are observed at H-SF similar to 0.5 kOe, suggesting a competing ordered state under magnetic fields below T-C. Remarkably, a second shoulder is observed at similar to 1 kOe in the dM/dH-vs-H curve, revealing another metastable spin-ordered state in Cu2OSeO3. This state is retained and enhanced by applying pressure. As H rises to 55 T, no further slope changes in the M-H curve are observed. These magnetic properties indicate a complex spin orientation in the geometrically spin-frustrated system Cu2OSeO3.

Colossal magnetoresistance (CMR) and electroresistance (CER) induced by the electric field in spinel multiferroic CdCr2S4 are reported. It is found that a metal-insulator transition (MIT) in CdCr2S4 is triggered by the electrical field. In magnetic fields, the resistivity of CdCr2S4 responds similarly to that of CMR manganites. Combing previous reports, these findings make CdCr2S4 the unique compound to possess all four properties of the colossal magnetocapacitive (CMC), colossal electrocapacitive (CEC), CER, and CMR. The present results open a new venue for searching new materials to show CMR by tuning electric and magnetic fields., Comment: 3 pages, 4 figures, accepted by Applied Physics Letters

The RMn2O5 (R=Pr, Nd, Sm, and Eu) oxides showing magnetoelectric (ME) behavior have been prepared in polycrystalline form by a standard citrate route. The lattice parameters, obtained from the powder XRD analysis, follow the rare-earth contraction indicating the trivalent character of the R ions. Cusp-like anomalies in the magnetic susceptibility curve and sharp peaks in the specific heat were reported at the corresponding temperatures in RMn2O5 (R=Pr, Nd, Sm, and Eu) indicating the magnetic or electric ordering transitions., 2 pages, 1 table, 3 figures, will be published in the Proceedings of the 24th International Conference on Low Temperature Physics

Low-temperature specific-heat data C(T) of two Na0.35CoO2. 1.3H2O samples (I and II) with temperature T down to 0.6 K without and with magnetic field of 8 T are presented. The normal-state linear coefficient of specific heat γn, Debye temperature ΘD, superconducting transition temperature Tc, specific heat jump at Tc, ΔC/γnsTc, and superconducting volume of fraction (SVF) are 14.89 mJ/mol K2, 503, 4.7 K, 1.96, and 26.6% for sample I and 13.94 mJ/mol K2, 362, 4.5 K, 1.45, and 47.4% for sample II, respectively. Because the superconducting properties may depend on the water content of sample, it is found that the better quality (higher SVF) of sample, the nodal order parameter is better than BCS isotropic s-wave model in describing the gap function of this interesting compound Na0.35CoO2. 1.3H2O.

A detailed study of the magnetic properties has been carried out for the LuFe2O4 system. Room temperature X-ray diffraction indicated single phase of the polycrystalline powder. The dc magnetization reveals the magnetic transition near 225 K. The ac susceptibility showed a peak corresponding to the magnetic transition; however, the peak is found to be frequency-dependent. With increasing frequency, the peak-temperature of the real part of the ac susceptibility (X') increases and the respective susceptibility values are decreased. The imaginary part of the ac susceptibility (X) increases with increasing frequency and so as the magnetic peak-temperature. The dynamic scaling of the ac susceptibility reveals the spin glass nature of this phase. The unusual glassy nature of the magnetic transition seems to be related to the presence of fractional disorder of the Fe2+ and Fe3+ ions resulted from the oxygen nonstoichiometry.

Dynamic dielectric properties were studied on the newly discovered multiferroic spinel, CdCr2S4. Two single crystals, grown under the same condition but from different batches were used, which showed identical behavior. Frequency-dependent dielectric constant as a function of temperature ('(ω)) exhibits relaxation behavior only below ferromagnetic transition temperature, TC ~ 84 K, which indicated that the charge dipoles were associated with ordered magnetic spins. By fitting with extended Debye model (Cole-Cole equation), the relaxation characteristic time (τ) at different temperatures was obtained. When 55 < T < 84 K, the τ value decreases with decreasing temperature. It is somehow unusual as it doesn't obey the thermal activation model (Arrhenius law). These results suggest that the relaxation behavior is strongly affected by spin not by thermal fluctuation. Different ac voltages were also selected to study the field effect on the relaxation behavior. For Vac = 20 V, '(ω) dramatically changes and τ value becomes difficult to obtain as T < 55 K, suggesting that some unknown phases could exist below 55 K. Complex relaxation behavior below TC could be originated from the coupling among spin, lattice and dipole via exchangestriction.

This article demonstrates that a visible light active N-doped TiO 2 film can be fabricated by atomic layer deposition (ALD) with titanium chloride and ammonia water as the precursors. A 1.60 atom % N-doping anatase TiO 2 film has been successfully grown on an n + -silicon substrate. The ratio of substitutional N doping to the total N doping as high as 70% is achieved that extends the long-wavelength cutoff of TiO 2 to 550 nm. Results from the analysis of incident photon-to-current efficiency and potential-dependent photocurrent density suggest that the visible light activity of ALD N-doped TiO 2 films can be further improved by reducing the carrier recombination rate and increasing optical absorption efficiency. © 2008 The Electrochemical Society. [DOI: 10.1149/1.2968951] All rights reserved.