Electron Spin Resonance in a Spin-1/2 Heisenberg Strong-rung Ladder

Cu(C$_8$H$_6$N$_2$)Cl$_2$, a strong-rung spin-1/2 Heisenberg ladder compound, is probed by means of electron spin resonance (ESR) spectroscopy in the field-induced gapless phase above $H_{c1}$. The temperature dependence of the ESR linewidth is analyzed in the quantum field theory framework, suggesting that the anisotropy of magnetic interactions plays a crucial role, determining the peculiar low-temperature ESR linewidth behavior. In particular, it is argued that the uniform Dzyaloshinskii-Moriya interaction (which is allowed on the bonds along the ladder legs) can be the source of this behavior in Cu(C$_8$H$_6$N$_2$)Cl$_2$

The research of qualitative indicators of gas pipelines during the operation

The operation of gas pipelines is a complex of technical measures, aimed at preservation of the main stock of gas pipeline transportation facilities. The purpose of these measures is to maintain and to restore the initial operational capabilities of gas pipelines, in general and in particular areas. The line section of gas pipelines has the largest size and cost. Naturally determined process of changing the quality of gas pipelines during the operation is accompanied by the accumulation and development of damages, failures; this determines the objective need to restore the quality of operation. The practical running of the line section of gas pipelines is characterized by a certain flow of failures; therefore it is necessary to ensure the required level of reliability of the gas pipeline during the entire period of operation. The quality control study of the inter-settlement gas pipeline section was conducted, and graphs of dependence of gas pipeline quality parameters on time were presented in the work.Keywords: line section of the gas pipeline, technological state, failures in operation, gas pipeline operation, control and quality parameters of the gas pipeline

Pressure-driven gapped-to-gapless phase transition in a quantum antiferromagnet with large planar anisotropy

Strongly correlated electron systems can be driven to quantum critical points via various routes. Contrary to field-induced transitions of a gapped quantum antiferromagnet into the gapless ordered state (characterized by the $z=2$ dynamic critical exponent and a quadratic excitation dispersion), pressure-induced instabilities possess $z=1$ and a linear excitation spectrum, belonging to another universality class. Employing radio-frequency susceptibility technique, we demonstrate that in the tetragonal easy-plane quantum paramagnet NiCl$_2$$\cdot$4SC(NH$_2$)$_2$ (aka DTN) the spin gap vanishes at about $4.3$ kbar, suggesting the onset of antiferromagentic order induced by pressure. Powder neutron diffraction measurements confirm that no lattice distortion occurs at this pressure and that the high spin symmetry is preserved. We are able to quantitatively describe the pressure-driven evolution of the critical fields and spin Hamiltonian parameters in DTN. The studies are complemented by high-pressure electron spin resonance measurements confirming the proposed scenario.Comment: Main text: 11 pages, 6 figures Supplement: 6 pages, 4 figure

Spin correlations in the frustrated ferro-antiferromagnet SrZnVO ( PO 4 ) 2 near saturation

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Low-temperature magnetic structure and electron paramagnetic resonance properties of the quasi-one-dimensional S = 1/2 Heisenberg helimagnet CuCl2Cl_{2} ⋅ 2 NC5C_{5}H5H_{5}

International audienceWe present results of electron paramagnetic resonance (EPR) and neutron-diffraction studies of Cu$Cl_{2}$ ⋅ 2 N$C_{5}$$H_{5}$, which is regarded as one of the best known uniform spin-1/2 Heisenberg antiferromagnet chain systems. We reveal that at $T_{N}$=1.12 K, Cu$Cl_{2}$ ⋅ 2 N$C_{5}$$H_{5}$ undergoes the transition into the magnetically ordered spiral state with Q=(0.5,0.4,0.5) r.l.u. It was shown that the zigzag interchain interactions result in a noticeable geometrical frustration, also affecting the ordered moment per $Cu^{2+}$ and EPR properties, including the angular dependence of the linewidth. The temperature dependencies of the EPR parameters are discussed

Spin Density Wave versus Fractional Magnetization Plateau in a Triangular Antiferromagnet

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