Reversal transient laser-induced voltages in La2/3Ca1/3MnO3 films

This paper reports that the transient laser-induced voltages have been observed in La2/3Ca1/3MnO3 thin films on MgO （001） in the absence of an applied current. A peak voltage of - 0.15 V was detected in response to 0.015J pulse of 308 nm laser. It is demonstrated that the signal polarity is reversed when the films are irradiated through the substrate rather than at the air/film interface. Off-diagonal thermoelectricity may support the inversion of the signal when the irradiation direction is reversed.     

Cusps in KL→3π decays

The pronounced cusp in K→3π decays which is generated by the pion mass difference is directly related to the ππS-wave scattering lengths. We apply a nonrelativistic effective field theory framework to evaluate the amplitudes for K_L→3π decays in a systematic manner. Electromagnetic effects in the neutral channel K_L→3π⁰ are also discussed.     

Electric and magnetic behaviour in double doped La2/3＋4x/3Sr1/3-4x/3Mn1-xMgxO3

The double-doped La2/3＋4x/3Sr1/3-4x/3Mn1-xMgxO3 samples with fixed Mn^3＋/Mn^4＋ ratio equal to 2/1 are investigated by means of magnetism and transport measurements. Phase separation is observed at temperature higher than T^onset c for x = 0.10 and 0.15. For x = 0.10, rather strong phase separation induces drastic magnetic random potential and results in the localization of carriers. Thus, the varlable-range hopping process dominates. For other samples, there is no or only weak phase separation above T^onset c. Thus, thermal activation mechanism is responsible for the high temperature transport behaviour. For x = 0.20 and 0.25, unexpected AFM behaviour is observed at low temperature. All these results are well understood by considering the special role of the ＂double-doping＂.     

Spin Hall Magnetoresistance in Pt/BiFeO3 Bilayer

Multiferroic materials are general antiferromagnets with negligibly small net magnetization, which strongly limits their magnetoelectric applications in spintronics. Spin Hall magnetoresistance(SMR) is sensitive to the orientation of the Néel vector, which can be applied for the detection of antiferromagnetic states. Here, we apply SMR on the unique room-temperature antiferromagnetic multiferroic material BiFeO₃(BFO). The angular dependence of SMR in a bilayer of epitaxial BFO(001) an...     

Spectroscopic properties in Er3＋/yb3＋ Co-doped fluorophosphate glass

Using the technique of high-temperature melting, a new Er3＋/Yb3＋ co-doped fluorophosphate glass was prepared. The absorption and fluorescence spectra were investigated in depth. The effect of Er3＋ and Yb3＋ concentration on the spectroscopic properties of the glass sample was also discussed. According to the Judd Ofelt theory, the oscillator strength was computed. The lifetime of 4113/2 level （t-m） of Er3＋ ions was 8.23 ms, and the full width at half maximum of the dominating emission peak was 68 nm at 1.53 μm. The large stimulated emission cross section of the Er3＋ was calculated by the McCumher theory. The spectroscopic properties of Er3＋ ion were compared with those in different glasses. The full width at half maximum and σe are larger than those of other glass hosts, indicating this studied glass may be a potentially useful candidate for high-gain erbium-doped fiber amplifier.     

Kinetics of the phase transition in crystals PbIn1/2Nb1/2O3–PbMg1/3Nb2/3O3–x PbTiO3

The time dependences of the optical transmission, velocity of sound, and elastic constants at room temperature in a number of the [001]-oriented PbIn_1/2Nb_1/2O₃–PbMg_1/3Nb_2/3O_3–x PbTiO₃ single crystals with the compositions lying both far from the morphotropic phase boundary and in its vicinity have been investigated. The analysis of the data obtained has been carried out. It has been shown that, in all the studied crystals, phase transitions induced by an electric field occur in two stages: the first stage is an incubation period associated with a small increase in the polarization of a part of the sample being in the glass phase, and the second phase (after the incubation period τ) is a rapid increase in the polarization and the formation of a long-range order. It has been found that the time τ depends on how close is the temperature of measurements to the Vogel–Fulcher temperature T _f . The closer is the temperature of measurements to the Vogel–Fulcher temperature T _f , the weaker is the electric field required to be applied to the sample in order to induce a ferroelectric phase. It has been demonstrated that the phase state of the studied crystals is unstable, which manifests itself in a strong dependence of the incubation period τ on the time between the annealing of the sample and the beginning of the measurements. The stability of the phase state depends on the PbTiO₃ concentration: an increase in the concentration leads to a significant increase in the stability.     

Phase separation in Sr doped BiMnO3

Phase separation in Sr doped BiMnO3 （Bil_xSrxMnO3, x = 0.4-0.6） was studied by means of temperature-dependent high-resolution neutron powder diffraction （NPD）, high resolution X-ray powder diffraction （XRD）, and physical property measurements. All the experiments indicate that a phase separation occurs at the temperature coinciding with the reported charge ordering temperature （Tco） in the literature. Below the reported TCO, both the phases resulting from the phase separation crystallize in the orthorhombically distorted perovskite structure with space group Imma. At lower temperature, these two phases order in the CE-type antiferromagnetic structure and the A-type antiferromagnetic structure, respectively. However, a scrutiny of the high-resolution NPD and XRD data at different temperatures and the electron diffraction exper- iment at 300 K did not manifest any evidence of a long-range charge ordering （CO） in our investigated samples, suggesting that the anomalies of physical properties such as magnetization, electric transport, and lattice parameters at the TCO might be caused by the phase separation rather than by a CO transition.     

Spin-glass-like behaviour and positive magnetoresistance in oxygen deficient La2/3Ca1/3MnO3-δ thin films

The magnetism and magnetoresistance (MR) in a series of oxygen-deficient La_{2/3}Ca_{1/3}MnO_{3-δ} (LCMO) thin films have been investigated. Compared with the films with stoichiometric oxygen concentration, the oxygen-deficient LCMO thin films show a spin-glass-like behaviour at low temperatures, and a positive MR effect above the metal－insulator transition temperature. The mechanism of such unusual phenomena is discussed.     

Effects of Yb^3＋ in Er^3＋/Yb^3＋ Codoped Fluorophosphate Glasses

For the Er^3＋ /Yb^3＋ codoped fluorophosphate glasses, Judd-Ofelt theory is used to analyse the influence of YbF3 as not a sensitizer but an average component on the spectroscopic properties around 1530nm emission. The double roles of Yb^3＋, as a sensitizer and as an average component, are discussed. It is found that Yb^3＋ as an average component contributes to the increase of fluorescence lifetime, and Yb^3＋ as a sensitizer has the best sensitization when its concentration is 2.4 mol%.     

Superparamagnetism and spin-glass-like behavior in (La1−xTbx)2/3Ca1/3MnO3 Perovskite

The magnetic and magnetotransport properties of a series of (La_1−xTb_x)_2/3Ca_1/3MnO₃ oxides have been investigated. Substitutions ranging from x=0.0 to 0.4 have been used. In the largest 〈r_A〉 region, only ferromagnetism is observed. As 〈r_A〉 decreases, there is a transition from ferromagnetic to spin-glass order. As 〈r_A〉 decreases further, the ferromagnetism will completely disappear and a direct transition from superparamagnetic to spin-glass order will occur on cooling.     

Upconversion Luminescence Dynamics in Er^3＋/Yb^3＋ Codoped Nanocrystalline Yttria

The upconversion luminescence and dynamics in Er^3＋ /Yb^3＋ codoped nanocrystalline yttria （7-65 nm） are studied under 980-nm pulsed laser excitation, It is found that the red emission of ^4F9/2-^4I15/2 and the green emission of ^2H11/2/^4S3/2 in nanoparticles with lower concentration of Yb^3＋ result from a two-photon excitation, In nanocrystals with higher Yb^3＋ concentration, the red emissions from a two-photon excitation, while the green emissions from a three-photon excitation, The luminescence dynamics indicates that as the particle size decreases, both the rise and the decay time constants become shorter, As the size decreases to several nanometres, the rise process nearly disappears, suggesting that the upconversion luminescence originates mainly from self-excitation of Er^3＋, instead of the energy transfer of Yb^3＋→ Er^3＋.     

Extra-Large Magnetoresistance in Fe/In2O3 Granular Films

Nanogranular Fe0.35/(In2O3)0.65 films with complex magnetic structure were prepared by the rf sputtering method.An extra-large magnetoresistance up to 506% was obtained at 2.2K,which is two orders of magnitude larger than that obtained at room temperature.This is related to the interaction with the impurities influencing the local magnetization,which is quite different from the spin-dependent tunnelling effect at room temperature.The interspacing Fe atoms dispersed in the In2O3 matrix play an important role in the transportation properties of carriers at low temperature.     

Enhancement of up-conversion Yb3＋/Tm3＋/Er3＋ tri-doped tellurite glass luminescence properties in transparent oxyfluoride ceramics

Optically transparent Er3＋/Tm3＋/Yb3＋ tri-doped oxyfluoride tellurite based nano-crystallized glass ceramics with the batching composition of 73TeO2-15ZnO-7ZnF2-3YF3-1.5YbF3-0.3ErF3-0.2TmF3 （mol%） is prepared by a conventional melting quenching and the subsequent heat treatment processes. The sizes of grown nano-crystals in glass matrix appear to be smaller than 100 nm from the scanning electron mi- croscope measurement. Visible up-conversion luminescence of the as melted glass and glass ceramics is investigated. The three-color up-conversion luminescence intensities by 980-nm pumping are increased significantly due to the heat treatment, and the blue intensity increases with a higher magnitude than other wavelengths after heat treatment.     

Thermal Hysteresis in La2/3 Ca1/3 MnO3 Films Grown on Tilted SrTiO3 Substrates and Influence of External Magnetic Field

Thermal hysteresis in the resistivity of La2/3 Cu1/3MnO3 thin films grown on tilted SrTiO3 substrates is simulated by using the random network model on the basis of mixed-phase percolation between metallic and insulating domains, The metallic-insulating transition temperatures during the warming process are lower than those during the cooling process due to the difference in fraction of metallic domains between warming and cooling process. With an external magnetic field, the metallic-insulating transition temperatures shift to a higher value and the resistivities are reduced. The excellent agreement between the simulation and the experimental data further verifies that phase separation plays a crucial role in the transport process of La2/3Ca1/3MnO3 thin films.     

Induced Phase Transition in PbMg1/3Nb2/3O3–xPb(Zr0.53Ti0.47)O3 Transparent Ceramics

Physics of the Solid State - Time dependences of permittivity and optical transmission in the Pb(Mg1/3Nb2/3)O3–xPb(Zr0.53Ti0.47)O3 (x = 16, 23, and 33%) transparent ferroelectric ceramics are...     

Effect of polarization on the intensity of anomalous electron emission in the (1 ? x)PbMg1/3Nb2/3O3 + xPbTiO3 system

Spectra of anomalous electron emission from the surface of solid solutions in the (1 − x)PbMg_1/3Nb_2/3O₃ + xPbTiO₃ system with x = 0.06, 0.10, 0.13, 0.20, and 0.25 have been studied. While the energy characteristics of the anomalous electron emission spectra vary monotonically with x, the behavior of integrated intensity was found to be nonmonotonic with a maximum occurring at x = 0.1. According to the proposed interpretation, the results obtained are explained by the effect of the potential barrier on the electron emission; the potential barrier depends, in turn, on the permittivity ε of the samples. Original Russian Text ? A.T. Kozakov, A.V. Nikol’skiĭ, V.P. Sakhnenko, A.N. Pavlov, V.G. Smotrakov, V.V. Eremkin, 2009, published in Fizika Tverdogo Tela, 2009, Vol. 51, No. 7, pp. 1310–1314.     

Maximum-entropy TFμSR study of vortex states in 1/2/3 cuprates

A maximum-entropy (ME) method has been applied to TFSR vortex data of RBa₂Cu₃O₇ (R1237; R=Er, Gd and Eu). The obtained information on the field distribution is of much better quality than that resulting from Fourier transformation and curve-fitting of the same data. ME application to R1237 TFSR data taken below T_c at LAMPF show asymmetrical, nearly triangular, field distributions, which broaden with decreasing temperature. Significant deviations from Abrikosov predictions have been observed for the estimated R1237-vortex field distributions. Below 10 K, for Er1237 and Gd1237, the non-Abrikosov features appear to be influenced by the rare-earth magnetism. The low-field tail in the field distribution and the ME-intensity anomaly near T_c suggest glassy features in the 1/2/3 cuprate vortex states.     

Charge density wave in kagome superconductor AV3Sb5

The kagome lattice is one of the most important platforms to investigate quantum many-body physics.For example,owing to its special lattice,the kagome lattice has a standard geometric frustration phenomenon in quantum magnetism.How to utilize this simple lattice to uncover the unconventional quantum phenomenon attracts great attention.     

Strain-enhanced polarization sensitivity in β-Ga2O3 photodetector

Polarization-sensitive photodetection and imaging have great application value in fields such as polarization division multiplexing optical communication, remote sensing, near-field imaging and military monitoring. Pursuing a high polarization ratio has always been the research hotspot in polarization-sensitive photodetectors. In this paper, we report a compression strain enhanced polarization ratio in β-gallium oxide(β-Ga₂O₃) single crystal flake. A rigorous crystallograph...     

The transverse laser induced thermoelectric voltages in step flow growth （1-x）Pb(Mg1/3Nb2/3)O3-xPbTiO3 thin films

This paper reports that the transverse laser induced thermoelectric voltages (LITV) are observed for the first time in the step flow growth (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT,x = 0.20, 0.33, 0.50) thin films deposited on vicinal-cut strontium titanate single crystal substrates. Because lead magnesium niobate-lead titanate is a solid solution of lead magnesium niobate (PMN) and lead titanate (PT), there are two types of signals. One is wide with a time response of a microsecond, and the other superimposed with the wide signal is narrow with a time response of a nanosecond. The transverse LITV signals depend on the ratio of PMN to PT drastically. Under the irradiation of 28-ns pulsed KrF excimer laser with the 248-nm wavelength,the largest induced voltage is observed in the 0.50Pb(Mg1/Nb2/3)O3-0.50PbTiO3 films. Moreover, the effects of film thickness, substrates, and tilt angles of substrates are also investigated.