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1.
We report synthesis and characterization of new Sr2ZrMnO6 manganite-like material. Samples were produced by the solid state reaction method with sinterization temperatures up to 1400 °C. X-ray diffraction experiments reveal that structure belongs to the perovskite system, space group . Lattice parameter was obtained by means of Rietveld-type refinement, through the GSAS code. Magnetic properties were studied by using an MPMS Quantum Design SQUID. From measurements of magnetization as a function of temperature, we determine the occurrence of a paramagnetic–antiferromagnetic transition with Néel temperature 50 K. Curie–Weiss fitting permitted to obtain the magnetic characteristic parameters. At temperature regimes below the Néel temperature, strong evidences of frustration and an irreversibility temperature between zero field cooling (ZFC) and field cooling (FC) measurements were observed. Curves of magnetization as a function of applied field were performed at . Results show a hysteretic feature for Sr2ZrMnO6 magnetic material. This response is attributed to formation of magnetic clusters as a consequence of cationic (magnetic and no magnetic) disorder along the double perovskite structure. 相似文献
2.
Recent reports on superconductivity in parent compounds [RE = Pr, Nd, Sm, Eu, Gd] prepared by metal-organic decomposition (MOD) shed new light on the electronic and magnetic phase diagram of electron-doped cuprates. A thorough reduction process is the key to inducing superconductivity in square-planar coordinated cuprates. In this work, Pr2CuO4 films were grown epitaxially by molecular beam epitaxy (MBE) on (001)SrTiO3, (110)GdScO3 and (110)DyScO3 substrates. A modified two-step reduction process is required in order to obtain single-phase superconducting samples. The optimized superconducting properties are , while the room-temperature resistivity is about . Hence, we show that even amorphous Pr2CuOy films deposited on (110)DyScO3 become superconducting after the application of the two-step annealing process. These results indicate that superconductivity is induced to Pr2CuO4 by systematic optimization of the reduction conditions, irrespective of the synthesis route. 相似文献
3.
The electronic structure and elastic properties of a double perovskite slab-rocksalt layer compounds of Eu2SrAl2O7 were calculated by local- (spin-) density approximation [L(S) DA] band theory with Hubbard term of U. We used and for the calculations. The band gap of Eu2SrAl2O7 is 4.8 eV. Both of Eu-O and Al-O bonds have strong covalent character and Sr-O is a perfect ionic bond. The full set elastic constants indicate the elastic modulus of Eu2SrAl2O7 is 224 and 240 GPa by calculation and experiment, respectively. 相似文献
4.
G. Seyfarth D. Jaccard A. Krzton-Maziopa K. Conder 《Solid State Communications》2011,151(10):747-10708
We report measurements of the temperature and pressure dependence of the electrical resistivity (ρ) of single-crystalline iron-based chalcogenide Cs0.8Fe2Se2. In this material, superconductivity with a transition temperature develops from a normal state with extremely large resistivity. At ambient pressure, a large “hump” in the resistivity is observed around 200 K. Under pressure, the resistivity decreases by two orders of magnitude, concomitant with a sudden Tc suppression around . Even at 9 GPa a metallic resistivity state is not recovered, and the ρ(T) “hump” is still detected. A comparison of the data measured upon increasing and decreasing the external pressure leads us to suggest that the superconductivity is not related to this hump. 相似文献
5.
6.
Magnetic susceptibility of powder Er2Ti2O7 (ErT) is measured between 300 K and 80 K. shows a Curie-Weiss (CW) type behaviour with ErTiO3.5 and . A crystal field (CF) analysis of our experimental data, g-values (g∥=0.27 and g⊥=7.8) and the positions of two CF levels (reported earlier from an inelastic neutron scattering study) provide CF parameters and CF levels of the ground 4I15/2 and excited multiplets of ErT. The theoretical follows a CW-type behaviour, with . Single-ion magnetic anisotropy (χ⊥−χ∥) is 9500×10−6 emu/mol ErTiO3.5 at 300 K, which increases by ∼54 times at 10 K and ErT resembles an XY planar system. It can be inferred from CF analysis that the earlier observed change of from −13 K to −22 K below 50 K is not due to the CF effect. Nuclear hyperfine (HF) levels of 167ErT and 166ErT are calculated and the theoretical curve of vs. T (K) for T<TN matches the observed results. Mössbauer lines expected for 166ErT are also predicted. 相似文献
7.
L.T. Corredor J. Velasco Zrate D.A. Landínez Tllez F. Fajardo J. Arbey Rodríguez M. J. Roa-Rojas 《Physica B: Condensed Matter》2009,404(18):2733-2735
We report experimental and theoretical study of crystallographic lattice and electronic structure of Sr2GdRuO6 complex perovskite, which is used as precursor in the fabrication process of superconducting ruthenocuprate RuSr2GdCu2O8. Samples were produced by the standard solid state reaction. Rietveld refinement of experimental X-ray diffraction patterns shows that material crystallizes in a monoclinic structure, which belongs to the P21/n (#14) space group, with lattice parameters , , , and tilt angle β=90.258. Calculations of electronic structure were performed by the density functional theory. The exchange and correlation potentials were included through the LDA+U approximation. Density of states (DOS) study was carried out considering the two spin polarizations. Results show Gd are majority responsible for the magnetic character in this material, but Ru contribution is also relevant because d-orbital is closer to Fermi level. Theoretical results evidence that Sr2GdRuO6 material behaves as a magnetic semiconductor, with 20μB effective magnetic moment. 相似文献
8.
The physical properties of La0.5Ba0.5FeO3 perovskite have been investigated. The resistivity and magnetism change at around the charge disproportionation temperature. The ferromagnetic cluster-glass state appears when . Under 5 kbar pressure a new phase transition at 5.5 K is found in the magnetization measurement. The transition temperature increases with the increase of the applied pressure. It is suggested that this transition is induced by the spin state transition from to with the pressure increase. 相似文献
9.
Effects of doping Na on the structure, electrical and magnetic properties of La2/3Ca1/3MnO3 are investigated. A structural phase transition from orthorhombic to rhombohedral structure takes place at y=0.375. All samples show metal-insulator (M-I) transition at the transition temperature and undergo the transition from paramagnetism to ferromagnetism at the Curie temperature TC. and TC increase monotonically with increasing Na content. However the Na-doped samples have a shoulder in their electrical transport curves found below and shows a widened magnetic transition process. On the other hand, intrinsic colossal magnetoresistance (CMR) peaks are observed in all the samples, but samples with y around 0.25 show two MR peaks which can be attributed to magnetic inhomogeneity induced by the doped Na+ ions. Here we propose a method to broaden the CMR peak of perovskite manganite, which is beneficial for practical applications. 相似文献
10.
This letter reports the novel nanostructure and excellent magnetic properties of Co19.35Fe53.28Hf7.92O19.35 films with varying thicknesses. Among the samples investigated, the film with a thickness of 432 nm exhibits the most excellent magnetic properties: high saturation magnetization, , low coercivity, , and high hard-axis anisotropy field of . The magnetic permeability remains almost stable up to 3 GHz and reaches a maximum at the ferromagnetic resonant frequency of 4.024 GHz. The excellent magnetic characteristics of this film in addition to a very high electrical resistivity of 3569 μΩ cm make it ideal for uses in high-frequency applications of micromagnetic devices. It reveals that these superior properties are ascribed to the formed peculiar nanostructure. A magnetic phase separation appears to occur strongly as the film thickness increases over 437 nm, which, in turn, modifies the high-frequency behavior. 相似文献
11.
Theoretical structure and surface energy of the reconstructed {01.2} form of calcite (CaCO3) crystal
Two different reconstructions of the (01.2) face (Ca or CO3 terminated) of calcite (CaCO3) were studied: (i) R1 reconstruction: the outermost layer is based on the [0 1 0] × 1/3[2 1 1] rectangular mesh, which is symmetrical with respect to the c glide plane of the crystal, thus fulfilling the 2D symmetry of the face and (ii) R2 reconstruction: the outermost layer is based on a lozenge shaped mesh that does not respect the 2D symmetry of the face.The , , and slabs geometry optimizations of calcite (CaCO3) were performed either at DFT level or by using empirical potentials; the results obtained with these two different calculation methodologies are in good agreement. With respect to their arrangement in the bulk, the CO3 groups of the outermost layer are significantly rotated about the crystallographic a-axis and about the normal to the 01.2 plane; further, the thickness of the outermost layer is significantly lower than that of the underneath ones.The surfaces energies (γ) at 0 K, for relaxed and unrelaxed , , and faces, were determined either at DFT level or by using empirical potentials. Independently of the method of calculation employed, the stability order of the relaxed faces is < < < . Concerning the unrelaxed faces, whose energies were evaluated by using empirical potentials only, the stability order is instead < < < ; such different ordering shows the importance of geometry relaxation in the calculation of the surface energy. The values of the relaxed surface energies are , , and erg/cm2. 相似文献
12.
Pressure dependence of the specific volume, V(P), of the recently discovered high-pressure compound Hf3N4 having cubic Th3P4-type structure (c- Hf3N4) has been measured at room temperature up to 43.9 GPa in a diamond anvil cell using energy-dispersive X-ray powder diffraction combined with synchrotron radiation. A least-square fit of the Birch-Murnaghan equation of state to the experimental V(P)-data yielded for c- Hf3N4 the bulk modulus of and its first pressure derivative of . For fixed at 4 the bulk modulus of c- Hf3N4 was determined to be . The obtained B0-value is only insignificantly below that estimated in preliminary measurements. Existing theoretical predictions for B0 scatter around the present experimental data. The observation of a high bulk modulus of c- Hf3N4 supports the suggestion that this compound could have high hardness. 相似文献
13.
K. Vijayanandhini 《Solid State Communications》2007,141(5):252-257
Phase-singular solid solutions of La0.6Sr0.4Mn1−yZnyO3−δ(0≤y≤0.3) [LSMZO] perovskite of rhombohedral symmetry (space group: ) with y up to 30 at.% could be synthesized notwithstanding the differences in ionic radii of MnV I3+ (i.r.=0.645 Å) and ZnV I2+ (i.r.=0.74 Å). The LSMZO≤02 compositions are ferromagnetic metallic (FMM) at room temperature whereas LSMZO-02-08 are ferromagnetic insulators (FMI) and LSMZO>08 are paramagnetic insulators (PMI). Total obliteration of the FM transition is unique to Zn-doping at leading to PMI even at low temperatures, measured up to 8 K (presently). The FM to PM transition (Tc) and the peak (Tp) in resistivity-temperature curves decreases with the Zn-content. The charge-transport in p-type LSMZO is predictable by variable range hopping (VRH), which changes to nearest-neighbor hopping of small polarons (NNHP) at T>Tp. Non-stoichiometry (0.005≤δ≤0.21) evaluated chemically from redox titrations indicated the prevalence of excess oxygen vacancy rather than charge compensatively predictable values which, in turn, indicates the diminishing Mn4+ content in LSMZO. The ’s act as electron donors in p-LSMZO and this increases the resistivity (ρRT) associated with the shift in Tc to low temperatures. Increased ρRT on annealing in low is a clear evidence on the role of in LSMZO. 相似文献
14.
Yuping Chen Rui Wu Xianglong Zeng Yuxing Xia Xianfeng Chen 《Optics & Laser Technology》2006,38(1):19-22
First-order type I quasi-phase-matched (QPM) blue second-harmonic generation was demonstrated in periodically poled LiNbO3 with period of 14.5 μm using d31. 52 μJ of harmonic blue light at 0.473 μm was generated pumped by 114 μJ 35 ps pulse laser at 0.946 μm at 150 °C with a conversion efficiency of 45.6%. The average conversion efficiencies of 41.3% and 19% were also obtained at 150 °C, respectively, in the conventional first- and third-order QPM blue second-harmonic generation at 0.473 μm. The temperature acceptance bandwidths of 20 mm length periodically poled LiNbO3 with first-order grating periods of 14.5 and 4.5 μm are 2.0 and 0.9 °C, respectively. The larger acceptance bandwidths and grating period for than those for enhance the frequency conversion efficiency, which shows the polarization dependence of quasi-phase matching. 相似文献
15.
M.K. Jacobsen G. Cao A.L. Cornelius 《Journal of Physics and Chemistry of Solids》2008,69(9):2237-2239
We have performed room temperature high pressure structural studies on the ferromagnetic perovskite SrRuO3 to 34 GPa. We have also used three different pressure media (silicone fluid, 4:1 methanol:ethanol and argon) to test for possible effects of pressure media on compression data. The orthorhombic perovskite structure is stable to the highest pressure, and the data can be fit with a bulk modulus of with a pressure derivative of for all of the pressure media. We have also examined the high pressure behavior of the RuO6 octahedra using a model that assumes the octahedra are not distorted. Various tilt angles around the ideal cubic perovskite axes are found and can be used to estimate the Ru-O-Ru bond angle that is known to be directly related to the ferromagnetic Curie temperature. For all pressure media, there appears to be a minimum in the Ru-O-Ru bond angle around 15 GPa. Implications for the observed high pressure magnetic behavior of SrRuO3 will be discussed. 相似文献
16.
We have succeeded in synthesizing two new lanthanum nitrides in a supercritical nitrogen fluid at high pressure (about 30 GPa) and high temperature (about 2000 K), using a diamond anvil cell and a YAG laser heating system. These nitrides were found to be stable down to 5 GPa and ∼300 K in a nitrogen atmosphere. One of the new lanthanum nitrides is a cubic P lattice-type phase, which is a main phase synthesized nitride. The calculated lattice parameter is at 5 GPa, 300 K. The other nitride is of a trigonal P lattice-type. The calculated lattice parameters are and at 5 GPa, 300 K. The most likely phase of the former new La nitride is , the structure of which may be similar to the Mn2O3-type (Ia80). The phase of the latter nitride is , the structure of which is the same as the La2O3-type (hP5). 相似文献
17.
The electronic density of states (DOS) and magnetic moments of rare-earth antimonides (RCrSb3) have been studied by the first principles full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). For the exchange-correlation potential, the LSDA+U method is used. The effective moments of LaCrSb3, CeCrSb3, NdCrSb3, GdCrSb3, and DyCrSb3 were found to be , , , and respectively. The exchange-splittings of Cr-3d state electrons and 4f-states of rare earth elements were analyzed to explain the magnetic nature of these systems. The Cr atom plays a significant role on the magnetic properties due to the hybridization between Cr-3d and Sb-5p state orbitals. The results obtained are compared and found to be in close agreement with the available data. 相似文献
18.
Yukihide Tsuji Toshimitsu Mochizuki andTohru Okamoto 《Physica E: Low-dimensional Systems and Nanostructures》2006,34(1-2):156
We have performed the in-plane magnetotransport measurements on the two-dimensional electron gas at the cleaved p-InAs (1 1 0) surface by deposition of Ag. The surface electron density Ns is determined from the Hall coefficient at . The coverage dependence of Ns is well explained by the assumption that each adsorbed Ag atom denotes one electron into InAs until the surface Fermi level reaches the adsorbate-induced donor level. The electron mobility μ is about and does not show a clear dependence on the coverage over . In the high-magnetic field regime of B>1/μ, Shubnikov–de Hass oscillations were observed. A beating pattern due to the strong spin–orbit interaction appears for high Ns. For lower Ns of , an apparent quantum Hall plateau for ν=4 and vanishing of the longitudinal resistivity were observed around . 相似文献
19.
Janusz Przes?awski Bogus?aw Kosturek Ryszard Jakubas 《Solid State Communications》2007,142(12):713-717
Thermal (specific heat) and optical (linear birefringence) studies were performed for a new ferroelectric crystal (C3N2H5)5Bi2Cl11. Two phase transitions were confirmed and described. The first-order paraelastic-ferroelastic phase transition at 360 K was studied with a polarizing microscope. The continuous second-order phase transition at 165 K to the ferroelectric phase is described by the Landau model using specific heat and linear birefringence data. The Landau expansion coefficients B and C are of an order of magnitude higher than the closely related ferroelectric crystal; MAPCB — (CH3NH3)5Bi2Cl11. Thermal parameters (such as the excess enthalpy and the excess entropy ) of the continuous transition were estimated and discussed. The ‘two-site’ model describing the motion of three of the five imidazolium cations, which is proposed from the structural studies, is fully confirmed by the data from the ac-calorimetric measurements. 相似文献