Equality of diagonal and non-diagonal microwave susceptibilities of EuO

The two elementsχ′ _yx andχ″ _xx of the magnetic susceptibility tensor for the cubic ferromagnetic EuO are investigated at microwave frequencies. It is shown that these two elements coincide when the magnetic field is large enough to remove the domain structure within the sample. This is in coincidence with theoretical predictions and shows a certain structure of the Hamiltonian. The magnetic transition temperature is found to beT _c=(69.2±0.2)°K in agreement with the result from specific heat measurement.     

Numerical simulations of isolated particles susceptibilities: effects of shape and size

We present here a sketch of some numerical results offered by a micromagnetism code based on the resolution of the Landau–Lifchitz equation. We have computed equilibrium configurations and dynamic susceptibilities to a weak field for magnetic materials with non-uniform magnetization and finite size and shape: cubic particles, finite-sized films with stripe domains and platelets with in-plane magnetocrystalline anisotropy. The obtained results have been compared with analytical models and experimental results. Some non-trivial effects have been pointed out (like surface modes) and fine details can be disclosed by susceptibility maps.     

The magnetic susceptibilities of NO and OH

A non-isothermal kinetic equation for the distribution function of a sub-system weakly coupled to a bath is derived by modification of the analysis and assumptions of a previous paper [1]. The equation has the form of a generalized non-isothermal Fokker-Planck equation when it is linearized in thermodynamic gradients and only terms through second order in the coupling parameters are retained. Higher order terms in the coupling parameter do not diverge with time. The equation is compared with certain ‘exact’ model results of Ullersma and with the coherence time method. The equation is used to calculate a jump rate for diffusion of a harmonic particle weakly coupled to a lattice and it is found that the jump rate becomes independent of the mass of the particle for a heavy enough particle. The source of the discrepancy of this result with a similar calculation of Prigogine and Bak is indicated. The model of the jump rate is inappropriate for diffusion in a thermal gradient and more appropriate models of the jump are briefly considered. A brief comparison of the derivation of the kinetic equation with the Fano coherence time approximation is made and a difference is noted.     

QCD susceptibilities and nuclear-matter saturation in a relativistic chiral theory

We investigate the evolutions with density of the QCD scalar susceptibility and of the sigma mass in a chiral relativistic theory of nuclear matter, in the mean-field approximation. In order to reach saturation we need to introduce the scalar response of the nucleons. The consequences are a quite mild density dependence of the sigma mass and the progressive decoupling of the quark density fluctuations from the nucleonic ones at large densities.     

Coupled-Hartree-Fock calculations of susceptibilities and magnetic shielding constants

Coupled Hartree-Fock calculations on the susceptibilities X and magnetic shielding constants σ are reported for the title molecules. Very large gaussian basis sets have been used in order to come sufficiently close to the Hartree-Fock limit. The basis set dependence of X and σ is discussed. In addition the applicability of two methods (maximum of X [20] and closure relations [21, 22]) for the prediction of the best gauge origins is investigated.

For C₂H₂, C₂H₄ aand C₂H₆ accurate theoretical results for the complete tensors of X and σ are given for the first time. For ethylene antishielding of σ _yy ^C is observed and illustrated by means of the induced electric currents.     

Initial magnetic susceptibilities of iron and nickel aerosol powders

The dependence on angle is considered for the hysteresis-free initial susceptibilities _a and _ar together with the initial susceptibility _o for iron and nickel aerosol powders, as well as the effects on these characteristics from changes in powder packing density. Estimates are made of the negative-interaction fields, and a quantitative comparison is made between the observed _ar() and theoretical values by means of the pair model. The correlation between the experimental and theoretical relationships confirms the concepts used on the predominant effects from magnetostatic interaction in the mechanism for magnetization reversal in powders of materials with low anisotropy.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, pp. 40–43, July, 1984.     

Intrinsic and extrinsic magnetic susceptibilities of some TCNQ complexes

The magnetic susceptibilities (χ) of quinolinium·(TCNQ)₂, N-methyl phenazinium·TCNQ and Li·TCNQ were measured from 2 to 300 K and are discussed in connection with the low-temperature specific heats (C) measured by other authors, χ is decomposed into three parts: χ_d the temperature-independent part, χ_c, Curie-Weiss type paramagnetism, and χ_p, the remainder. Correspondingly, C is composed of three terms, γT, H/T² and αT³. The electronic state of these substances is discussed in terms of each type of susceptibility.The model, on which the above separation of χ and C is based, defines two types of electrons: localized electrons associated with a magnetic moment and band electrons. Though this model is useful phenomenologically, it is shown that the analysis of χ on the basis of this model indicates less band electrons and more localized electrons or stronger magnetic interactions than does that of C.     

Optical and magnetic susceptibilities for semiconductors and alkali halides

Optical susceptibility, electronic polarizability and magnetic susceptibility values have been evaluated from optical electronegativities. The validity of the proposed empirical relations has been tested in the case of II–VI, III–V group semiconductors and alkali halides. The estimated values of these parameters are in good agreement with the available experimental data. There has been no report on the direct estimation of optical susceptibility and magnetic susceptibility using the concept of optical electronegativity.     

Magnetic structures and magnetic susceptibilities of terbium oxysulfide and oxyselenide

For the two isomorphous compounds Tb₂O₂S and Tb₂O₂Se, the magnetic susceptibility measurements on powder samples show an antiferromagnetic ordering with Néel temperatures of about 7.7 and 7K respectively. Differing in this respect from the other rare earth oxyselenides, the magnetic anisotropy of Tb₂O₂Se at low temperature is weaker than that of Tb₂O₂S.We also determine the magnetic structures of these two compounds by neutron diffraction experiments at 1.5K. The magnetic cell is orthohexagonal and doubled along the c-axis; the magnetic moments make an angle, with the c-axis, of 47 ± 10° for Tb₂O₂S and 30 ± 10° for Tb₂O₂Se and the moment values at 1.5K are 8.14 ± 0.2μ_B and 6.5 ± 0.2μ_B, respectively.It is rather exceptional that in a rare earth uniaxial compound the magnetic moment makes an angle with the c-axis. However we interpret this situation by the fact that several levels exist very near to the ground state. The crystal field calculations are in good agreement with the experimental results.     

Anomalous magnetic susceptibilities of the alkaline earth hexammines

The magnetic susceptibility of the metallic compounds Ca(NH₃)₆, Sr(NH₃)₆ and Ba(NH₃)₆ has been measured by the Faraday method in the range 2–200 K. The susceptibility of Ca(NH₃)₆ is strongly dependent on temperature and exhibits a broad minimum near 120 K and a peak near 10 K. In contrast to Ca(NH₃)₆, the susceptibilities of Sr(NH₃)₆ and Ba(NH₃)₆ are diamagnetic and decrease rapidly as the temperature is lowered. At low temperatures Ba(NH₃)₆ has the largest mass susceptibility of any nonsuperconducting metal.     

Structural,dielectric, electrical and magnetic properties of chemicothermally synthesized material: BiCaFeCeO6

In this communication, detailed studies of structural, micro-structural, dielectric, electrical (impedance, modulus and conductivity) and magneto-electric characteristics of a chemico-thermally synthesized sample of a double perovskite bismuth calcium iron cerate (BiCaFeCeO₆) have been reported. Preliminary structural analysis of room temperature X-ray diffraction data shows orthorhombic structure of the material. The homogeneous distribution of the grains of different dimensions (shape, size, etc) with a small number of voids observed in the scanning electron micrograph suggests the formation of high-density sample. Detailed analysis of dielectric and impedance experimental data, collected at different frequency and temperatures, have provided many important characteristics of the material, such as (a) grains, grain boundaries, and electrode dependent capacitive and impedance parameters, (b) co-relation between the structure, micro-structure and physical properties and (c) the relaxation characteristics of the tested samples. The nature of frequency dependence of AC conductivity of the material obeys the Jonscher's universal power law. The temperature dependence of conductivity provides the conduction mechanism in the material. Detailed studies of field dependence of electric polarization, magnetization and magneto-electric coefficient at room temperature exhibit the multiferroic characteristics of the material.     

The chiral magnetic effect: Beam-energy and system-size dependence

We consider the energy dependence of the local P and CP violation in AuAu and CuCu collisions over a large energy range within a simple phenomenological model. It is expected that at LHC the chiral magnetic effect will be about 20 times weaker than at RHIC. At lower energy range this effect should vanish sharply at energy somewhere above the top SPS one. To elucidate CME background effects a transport model including magnetic field evolution is put forward.     

Theoretical investigation of helix distortion and dielectric spectrum of antiferroelectric liquid crystals

Landau-Ginzburg equation is utilized to investigate the dielectric spectrum of an antiferroelectric liquid crystal (AFLC). Two collective modes, one associated with the in-phase motion at the low frequency side and the other related with the anti-phase motion at the high frequency side, are discussed in details utilizing the concept of bulk free energy of the material in terms of the pair interactions of two adjacent Smectic layers. The phenomenon of helix distortion related to the in-phase motion is observed theoretically based on the interlayer interactions of the AFLC system. The anti-phase mode related to the degree of the antiferroelectric ordering is also an important phenomenon depending on the layer-to-layer interactions. Finally we have theoretically obtained the critical field for helix unwinding with the model proposed by de Gennes.     

Electric and magnetic susceptibilities for a fluid-fluid interface: II. Critical behaviour

Formulae for the electromagnetic constitutive coefficients derived in a previous paper are used to analyse the critical behaviour of the reflectivities at normal and oblique incidence as well as the ellipsometric coefficient at the Brewster angle. Contributions due to correlations, which are neglected if one uses the average profile, are taken into account. Thus we e.g. calculate the energy losses due to scattering at the interface. We find that the ellipsometric coefficient contains the intrinsic thickness of the profile rather than the thickness of the average profile. For cyclohexane-aniline a comparison is made with recent experiments by Beaglehole.     

Quantum measurements and chiral magnetic effect

The effect of anisotropy for fluctuations of electric currents in magnetic field is addressed within framework of quantum measurements theory. It is shown that for free fermions in uniform magnetic field the anisotropy is of the same sign as one expects for chiral magnetic effect and is related to triangle anomaly. The corresponding decoherence functional contains anomalous off-diagonal terms leading to correlation of fluctuations between observables of opposite P-parity.     

Enantioseparation on a chiral nanostructured surface: Effect of molecular shape

In this paper we use the Monte Carlo simulation method to study adsorption of chiral molecules on a solid surface with periodic distribution of active sites. Namely, equilibrium adsorption of a racemic mixture of enantiomers represented by homonuclear tetramers is modeled on a square lattice with a chiral pattern of active sites. We consider two possible chiral structures of the tetramers which differ only by chain geometry but have equal adsorption energies. The effect of the chain geometry on the effectiveness of separation is assessed by comparing the corresponding adsorption selectivities obtained from the simulations. We present results of model calculations in which the parameters do not refer to any particular experimental system. These results indicate that the model chiral surface can, in general, adsorb preferentially the complementary enantiomer, regardless of its chain conformation. Specifically, it was shown that changes in the tetramer geometry, from S-shaped to -shaped, lead to marginal changes in the shape of both single component and mixed adsorption isotherms calculated for the enantioselective surface. In this context, the enantiomer separation on the surface proposed in this work was shown to be insensitive to molecular shape of the adsorbing species.     

On the calculation of the linear and quadratic dielectric susceptibilities of hexagonal silicon carbide

The electron and lattice contributions to the linear and quadratic dielectric susceptibilities of the hexagonal polytype of silicon carbide 2H-SiC are calculated within the Harrison bond-orbital model. The results obtained are in satisfactory agreement with the calculations performed by other authors and are close in order of magnitude to the corresponding values for the 6H-SiC polytype.