Magnetic order in the ternary compound NdRu2Ge2

Heat capacity, electrical resistivity and neutron diffraction studies have been performed on the tetragonal ternary compound NdRu₂Ge₂. Between temperatures of 17 and 10 K, the compound exhibits two types of sine-wave modulated magnetic structures, having wave vectors k = (0.19, 0.05, 0.125) and k = (0.12, 0.12, 0.0) with the amplitude of the moment along the c axis. Below 10 K, a first-order transition occurs to a ferromagnetic state with a moment of 3.64(13)μ_B aligned along the tetragonal axis.     

Possible existence of the ternary compound ZnCdSb2

Conclusions On the basis of these results, we can describe the formation of the ZnCdSb₂ phase in the following manner: an Sb atom in a deformed tetrahedron forms three real bonds with Sb (2.81 Å), Zn (2.65 Å), and Cd (2.81 Å); the fourth tetrahedral position is occupied by an unshared pair of antimony valence electrons. In this configuration the Zn-Cd bonds (2.93 Å) are virtual; this situation is, strictly speaking, responsible for the semiconducting properties of this phase.The maxima of the activation energy and thermal emf [24] at the ZnCdSb₂ composition are apparently due to a strengthening (an increase in directionality) of the Cd-Sb bonds during the formation of neighboring, shorter Zn-Sb bonds.Translated from Izvestiya VUZ. Fizika, No. 7, pp. 82–86, July, 1970.     

硅烯：一种新型的二维狄拉克电子材料

硅烯是单原子层的硅薄膜,其结构与石墨烯类似,由于其奇特的物理性质特别是狄拉克—费米特性,在近年来引起了人们的关注。文章简要介绍了硅烯这一全新的二维体系在实验上的一些进展,包括实现硅烯在表面上的外延生长,重构的结构表征和相变,狄拉克电子特性的证实,以及可能具有的超导转变等。     

硅烯:一种新型的二维狄拉克电子材料

要硅烯是单原子层的硅薄膜,其结构与石墨烯类似,由于其奇特的物理性质特别是狄拉克—费米特性,在近年来引起了人们的关注。文章简要介绍了硅烯这一全新的二维体系在实验上的一些进展,包括实现硅烯在表面上的外延生长,重构的结构表征和相变,狄拉克电子特性的证实,以及可能具有的超导转变等。     

MBE growth of a novel chalcopyrite-type ternary compound MnGeP2

Novel ternary Mn-containing compound MnGeP₂ has been grown on GaAs and InP substrates using molecular beam epitaxy, in which Mn and Ge were supplied from solid sources and P from a gas source. The films obtained showed XRD pattern characteristic of MnGeP₂. Lattice constants were determined using reciprocal lattice mapping analysis. Films directly grown on GaAs substrate showed three-dimensional grain-growth. By introduction of a Ge buffer layer growth mode became two-dimensional. The magnetization vs. temperature curve showed ferromagnetic properties at room temperature, in conflict with theory which predicts its antiferromagnetism. Presence of secondary phase is discussed.     

Optical properties of the ternary compound Tl Sb S2

We present an investigation of the near band-gap optical properties of TlSbS₂ between 2 and 300 K. We use both transmission and reflectivity measurements. The resolution of the first exciton line permits to obtain an accurate determination of the temperature coefficients of both the direct band-gap E₀ and the second threshold E₁. The absorption curves have been fitted according to the Toyozawa's model. We find a strong interaction with a phonon mode of energy 22 meV for both the E₀ and E₁ thresholds. The low temperature reflectivity spectra reveal clearly several direct transitions in the range 1.5–5.5 eV. All these structures have been identified as transitions between the highest valence band and the lowest conduction band.     

Magnetic properties of a new Kondo lattice compound: CePt2Si2

Measurements of magnetic susceptibility, electrical resistivity and specific heat on CePt₂Si₂ and LaPt₂Si₂ compounds are reported. Several anomalous properties are observed in CePt₂Si₂, characteristic of Kondo lattice and Fermi liquid systems with indication of coherence effects below 2 K.     

Spin fluctuations and magnetic order in the heavy fermion compound CePt2Sn2

We present zero and longitudinal field μ SR measurements of single crystal and polycrystalline specimens of the heavy fermion compound CePt₂Sn₂. Above 1 K the behaviour of the two samples is indistinguishable; the muon 1/T_1 increases with decreasing temperature until 25 K when it plateaus. The 1/T_1 relaxation rate differs strongly for the two cases below \sim\,0.8\ K. At 0.1 K a rate of about 20 μ s^-1 is seen in the polycrystal while in the single crystal it is only about 5 μ s^-1. Even more revealing is the fact that longitudinal field decoupling spectra at very low temperatures demonstrate an essentially static spin system to be present in the polycrystalline material while the single crystal shows definite dynamic spin properties. We conclude that, in the presence of the distortion, long range magnetic order occurs below 0.9 K while in tetragonal symmetry long range order is suppressed (probably due to frustration) and spin fluctuations remain for T\rightarrow0. This revised version was published online in July 2006 with corrections to the Cover Date.     

Absence of long-range magnetic ordering in the pyrochlore compound Er2Sn2O7

The low temperature behaviour of powder Er2Sn2O7 samples has been studied by magnetic susceptibility, heat capacity, and neutron scattering experiments. We report here the absence of magnetic ordering down to 100 mK. Anomalies in the heat capacity can be accounted for through an analysis of the crystal field spectrum observed by inelastic neutron scattering spectroscopy. These new measurements on Er2Sn2O7 suggest a new lower bound for the frustration index of f = |Θ(CW)|/T(N) = 14/0.1 = 140, placing this compound into a highly frustrated regime.     

New ternary superconducting compound La Ru_2As_2:Physical properties from density functional theory calculations

In this paper, we perform the density functional theory(DFT)-based calculations by the first-principles pseudopotential method to investigate the physical properties of the newly discovered superconductor LaRu_2As_2 for the first time.The optimized structural parameters are in good agreement with the experimental results. The calculated independent elastic constants ensure the mechanical stability of the compound. The calculated Cauchy pressure, Pugh's ratio as well as Poisson's ratio indicate that LaRu_2As_2 should behave as a ductile material. Due to low Debye temperature, LaRu_2As_2 may be used as a thermal barrier coating(TBC) material. The new compound should exhibit metallic nature as its valence bands overlap considerably with the conduction bands. LaRu_2As_2 is expected to be a soft material and easily machinable because of its low hardness value of 6.8 GPa. The multi-band nature is observed in the calculated Fermi surface. A highly anisotropic combination of ionic, covalent and metallic interactions is expected to be in accordance with charge density calculation.     

Crystallographic and magnetic properties of the U2.1Fe2Sn0.9 ternary stannide

A sample with global composition U_2.2Fe₂Sn was arc melted and annealed at 750°C. The crystal structure of the main phase obtained was refined assuming a tetragonal ordered version of the U₃Si₂-type structure (space group P4/mbm) down to a residual value of R_Bragg=0.0868 (R_F=0.0584). A final U_2.1Fe₂Sn_0.9 composition was obtained from the refinement.Magnetization, AC-susceptibility and ⁵⁷Fe Mössbauer results point to the existence of a small concentration of the U₅Sn₄ ferromagnetic impurity in the sample. No further magnetic transitions were observed down to 2 K. A strong hybridization of the 4s and/or 3d electrons of Fe is suggested from the low isomer shift values of Fe. A broad maximum in the magnetization at ∼125 K is observed, indicating spin–fluctuation features in this system.     

Optical effects in ternary and quaternary compound MESFETs

Light-generated voltages have been evaluated theoretically when the transparent gate of GaInAs and GaInAsP MESFETs is illuminated with optical radiation of varying intensities. Using these values the source-drain current under various light intensities has been calculated. Theoretical values of gain and optical gain as functions of the gate voltage for a given intensity are also presented for comparison.     

Fermi surface topology and the superconducting gap function in UPd2Al3: a neutron spin-echo study

We report on a single crystal neutron spin-echo investigation of the low-energy dynamic response in the heavy-fermion superconductor UPd2Al3 in the vicinity of the antiferromagnetic wave vector Q(0)=(0 0 0.5). Well inside the superconducting phase, antiferromagnetic quasielastic scattering, which is present in the normal state, is absent for relaxation times up to 10 ns, equivalent to an energy resolution of approximately 1 microeV. This places strong constraints on possible models for this magnetic superconductor.     

Temperature behavior of magnetization of DyCo2 compound

Zero field cooled (ZFC) and field cooled (FC) magnetization measurements were performed on the binary DyCo₂ cubic compound. Maxima for this compound were observed under ZFC magnetization. Below the broad maximum, irreversibility is observed. The magnetization curves for ZFC and FC regimes are split and magnetic moments for FC are higher than for ZFC. The dependence of the maxima upon the magnetic field and the time dependence of remanence is similar to the case of spin-glass-like systems.     

Observation of a new deformed structure in114Sn

Yrast as well as non-yrast states of¹¹⁴Sn have been investigated via the¹⁰⁰Mo(¹⁸O,4n) and the¹¹²Cd(,2n) reaction by means of in-beam-ray spectroscopy using the Compton-suppressed germanium detector array OSIRIS-Cube. A new rotational band including the band head with a tentative spin and parity assignment of 5^– could be placed in the level scheme and might be a candidate for ag ₉ ^2/–1 h_11/2 intruder band.     

Unexpected behavior in a two-path electron interferometer

We report the observation of an unpredictable behavior of a simple, two-path, electron interferometer. Utilizing an electronic analog of the well-known optical Mach-Zehnder interferometer, with current carrying edge channels in the quantum Hall effect regime, we measured high contrast Aharonov-Bohm (AB) oscillations. Surprisingly, the amplitude of the oscillations varied with energy in a lobe fashion, namely, with distinct maxima and zeros (namely, no AB oscillations) in between. Moreover, the phase of the AB oscillations was constant throughout each lobe period but slipped abruptly by pi at each zero. The periodicity of the lobes defines a new energy scale, which may be a general characteristic of quantum coherence of interfering electrons.