Antiferromagnetic insulating state in quasi-one-dimensional K2Cr3As3H

Quasi-one-dimensional(Q1D) Cr-based pnictide K₂Cr₃As₃ exhibits superconductivity probably with spin-triplet pairing. It is of fundamental importance to explore the parent compound from which superconductivity emerges. Here we report the synthesis,crystal structure, physical properties, and density functional theory(DFT) calculations of(nearly) fully hydrogenized K₂Cr₃As₃ H.It is found that the intercalation of hydrogen in K_2<...     

高Tc氧化物超导体Bi(Pb)-Sr-Ca-Cu-O(F)的“不可逆线”

研究了高T_c氧化物超导体Bi(Pb)-Sr-Ca-Cu-O(F)体系的“不可逆线”。发现不可逆磁场H^*<120Oe时,H^*=1590(1—t)^3/2;当120Oe*<1000Oe时,H^*=35700(1—t)^3/2-2480。指出H^*(T)曲线是一个磁通格子熔化线,在曲线以下属于磁通蠕动区;在H^*(T)与H_c2(T)之间属于磁通格子液态区,即磁通流动区。 关键词：     

“Hopf/homoclinic”簇放电和“SubHopf/homoclinic"簇放电之间的同步

以修正过的Morris-Lecar神经元模型为例,讨论了“Hopf/homoclinic”簇放电和“SubHopf/homoclinic"簇放电之间的同步行为.首先,分别考察了同一拓扑类型的两个耦合簇放电神经元的同步行为,发现“Hopf/homoclinic”簇放电比“SubHopf/homoclinic”簇放电达到膜电位完全同步所需要的耦合强度小,即前者比后者更容易达到膜电位完全同步.其次,对这两个不同拓扑类型的簇放电神经元的耦合同步行为进行了讨论.通过数值分析发现随着耦合强度的增加,两种不同类型的簇放电首先达到簇放电同步,然后当耦合强度足够大时甚至可以达到膜电位完全同步,并且同步后的放电类型更接近容易同步的簇放电类型,即“Hopf/homoclinic”簇放电.然而令人奇怪的是此时慢变量并没有达到完全同步,而是相位同步;慢变量之间呈现为一种线性关系.这一点和现有文献的结果截然不同.     

Electronic Transport and Magnetic Properties in Ferroelectric-Ferromagnetic Composites La5/8Ca3/8MnO3:ErMnO3

系统研究了xLa_5/8Ca_3/8MnO₃:ErMnO₃:(1-x)ErMnO₃(x=0、0.2、0.4、0.5、0.6、0.8、1)铁电铁磁复合材料的晶体结构和低温下的电磁输运性质.X光衍射结果表明金属铁磁相La_5/8Ca_3/8MnO₃和绝缘铁电相ErMnO₃由于晶体结构上的巨大差异几乎完全不相溶．电阻率随x的增大而降低,其导电特性可用经典的渗流理论来解释．当x>xc时,样品电阻特性由La_5/8Ca_3/8MnO₃主导,电阻温度曲线会出现金属绝缘体转变．磁性测试表明,由于xLa_5/8Ca_3/8MnO₃的掺入,复合材料的磁性相比单相ErMnO₃得到加强．从电磁性质综合分析认为这种复合材料是一种新的多铁性材料,相比单相多铁性材料ErMnO₃,它具有更强的磁性和更广的使用温度范围．     

An algebraic approach to (3, 3)⊕(3, 3)⊕(8, 8) chiral-symmetry breaking

We examine the Hamiltonian

$\text{H = H}{}_0\text{+ε}{}_0\text{u}{}_0\text{+ε}{}_8\text{u}{}_8\text{+A S}{}_{\mathrm{\alpha \alpha }}\text{+B d}{}_{\mathrm{8\alpha \beta }}\text{S}{}_{\mathrm{\alpha \beta }}$

, where u_o, u₈ belong to $\text{(3,}\text{3}\text{)+(}\text{3}\text{,3)}$ and S_αα, S_αβ belong to (8,8), following a purely algebraic approach due to Michel and Radicati and obtain B/A = 2√3 if ε₈/ε₀ = ?√2.     

NMR: hyperfine interactions in MoO3, MoS2, MoSe2 Mo3Se4, MoSi2 and Mo2C

Nuclear hyperfine interactions have been obtained by nuclear magnetic resonance (NMR) for in a number of binary Mo compounds, both insulators and metals, which illustrate the interplay between nuclear quadrupole and chemical (Knight) shift terms. The insulating phases are characterised by nuclear spin lattice relaxation times greater than 100 s, demonstrating the ineffectiveness of indirect phonon Raman relaxation for these compounds.     

利用超声脉冲回波重合法测定铌酸锂单晶弹性常数CijE和CijD

本文从基本的压电Christoffel方程出发导出三角晶系3m点群压电晶体弹性常数的表示式。并采用10MHz射频超声脉冲回波重合法测量了沿LiNbO₃不同对称方向传播的声速,结合e_ij和ε_ij⁵给出了LiNbO₃全部弹性常数C_ij^E和C_ij^D。它们是C₁₁^E=19.8 关键词：     

spin-lattice relaxation in cobalt-containing aluminophosphate molecular sieves

Phosphorus spin-lattice relaxation was studied in aluminophosphate molecular sieves containing various concentrations of either framework or non-framework cobalt. The behaviour of nuclear magnetisation in the presence of these paramagnetic centres was described successfully in the limit of no spin-diffusion. The diffusionless regime was strongly indicated with non-exponential magnetisation recovery and was therefore easy to recognise. According to the model, spin-lattice relaxation rates depend on the square of cobalt concentration. Measured relaxation rates agreed well with calculations if effective cobalt concentration was considered rather than the average one. The latter was obtained by bulk elemental analysis, while the former was extracted from cobalt concentration depth-profiles measured with Auger electron spectroscopy. These measurements indicated that in impregnated samples containing non-framework cobalt there could be much more cobalt near the crystal surface than within the crystal. Because high cobalt concentration can lead to an invisible phosphorus, only nuclei deep within the crystal contribute to the NMR signal. In such a case, the effective concentration is simply the concentration of cobalt far from the crystal surface. In our case, two impregnated samples with different bulk cobalt concentrations exhibited equal relaxation rates. Previously, such a case was misinterpreted as a case, in which nuclear spin-lattice relaxation was independent of cobalt concentration. AES measurements, however, revealed, that although average concentrations of the two samples were different by a factor of two, their effective concentrations were equal and thus in complete agreement with observed relaxation rates.     

Measurement of coherent pion-photoproduction on the 3He/3H isodoublet

Neutral and charged pion-photo production on ${}^3\text{H}$ and ${}^3\text{He}$ nuclei have been observed in the Δ(1232) resonance region. Resonance averaged cross-sections are presented as functions of momentum transfer.     

Exclusive photoproduction of mesons at HERA

The exclusive photoproduction reaction γp→p has been studied with the ZEUS experiment in ep collisions at HERA using an integrated luminosity of 468 pb⁻¹. The measurement covers the kinematic range 60<W<220 GeV and Q²<1 GeV², where W is the photon–proton centre-of-mass energy and Q² is the photon virtuality. These results, which represent the analysis of the full ZEUS data sample for this channel, are compared to predictions based on perturbative QCD.