Results For Susceptibilities Research Articles

Altered results for orbital and spin susceptibilities by inclusion of the diamagnetic contribution of the valence electrons in the evaluation of an Einstein de Haas experiment

The g-factor experiments of Huguenin et al. help to separate the spin and orbital susceptibility contributions of paramagnetic transition metals. In the evaluation of the experimental data, these authors took account of the Langevin diamagnetism of the core electrons whereas the valence electrons should be equally recognized for their diamagnetism. The introduction of this valence electron diamagnetism, obtained from band structure data, introduces significant changes of the results, leading to better agreement with other experiments and with theoretical results in most cases.

Decomposition of spin susceptibility of tetrathiafulvalenium-tetracyanoquinodimethanide (TTF-TCNQ) and analogous compounds

The method of separating the spin susceptibility, $\ensuremath{\chi}$, of tetrathiafulvalenium-tetracyanoquinodimethanide (TTF-TCNQ) and analogous quasi-one-dimensional compounds into the contributions of the individual chains by means of EPR data is reexamined in the light of more recent information on the compounds. For TTF-TCNQ it is concluded that, if proper consideration is given to the experimental uncertainties, the method can be used to obtain reliable qualitative results. For hexamethylene-tetrathiafulvalenium tetracyanoquinodimethanide (HMTTF-TCNQ), however, it is shown that the decomposition is unreliable since analysis of the data for different directions of magnetic field yields quite different results for the individual stack susceptibilities. It is suggested that the reason the decomposition does not work in this case, among others, is that the interstack interaction is too large. Recognizing these difficulties with the decomposition removes a number of apparent paradoxes or anomalies, such as: (1) the sign for thermoelectric power being opposite to the sign of charge of the carrier responsible for conduction; (2) $\ensuremath{\chi}$ for TTF being 5 or more times $\ensuremath{\chi}$ for tetraselenafulvalenium; (3) $\ensuremath{\chi}$ for the HMTTF chain being independent of temperature over the range where for all other chains investigated in this family it is not.

Van Vleck temperature independent susceptibilities in the rare earth double nitrates

Measurements of the magnetic susceptibilities between 4.2 and 1.1K of the rare earth zinc nitrates are reported. It is shown that the results for the Van Vleck temperature independent susceptibilities for cerium magnesium nitrate and cerium zinc nitrate are consistent with the published low lying level schemes for these two salts.

Electronic structure of intermetallic compounds with CsCl structure

Susceptibility, specific heat and Knight shift measurements as well as bandstructure calculations have been made for intermetallic compounds of the CsCl structure, ScB (where B is Ag, Cu, Pd, Rh, Ir, Ru), YRh and LaAg, to study the influence of filling the d shell of atom B. An analysis is given which yields quantitative results for the local susceptibilities, as characterized for the different angular momenta and sites of origin.

Adiabatic following model for two-photon transitions: Nonlinear mixing and pulse propagation

Two-photon resonantly enhanced parametric generation processes have generally been described using time-dependent perturbation theory. In this paper we show that a theory of two-photon coherent effects can be used to derive and explain these nonlinear mixing processes. Our technique makes use of the adiabatic following (AF) approximation to obtain solutions to a vector model describing the two-photon resonance. We show that the usual results for the nonlinear susceptibilities correspond to the $\stackrel{\ensuremath{\rightarrow}}{\mathrm{r}}$ vector of Feynman, Vernon, and Hellwarth adiabatically following the $\stackrel{\ensuremath{\rightarrow}}{\mathrm{\ensuremath{\gamma}}}$ vector in the small-angle limit. Consequently, the theory allows a natural extension to large angles, and power-dependent nonlinear susceptibilities are obtained. We then use these AF results for the polarization to study the propagation of pulses nearly resonant with a two-photon transition, and we demonstrate that the pulse reshaping is due to the two related effects of a nonlinear pulse velocity and self-phase modulation.

Uncoupled Hartree-Fock perturbation theory for the density matrix: the second-order properties of conjugated molecules

The Hartree-Fock perturbative approach to second-order properties is developed in terms of the uncoupled first-order density matrix. Apart from its theoretical interest, the present formulation is particularly suitable for computational purposes. The applications are to π-electron systems: a comparison with coupled results for dipole polarizabilities, magnetic susceptibilities and shielding is also given.

High-Low-Temperature Static Magnetic Properties of FeF2

The cluster variation method was applied to study static properties of the anisotropic uniaxial antiferromagnetic insulator FeF2. In particular the range of temperatures extending down to the spin-wave region was investigated. Theoretical results for spontaneous magnetization, longitudinal, and transverse susceptibilities, for example, were found to be in surprisingly good agreement with experiment for quite low temperatures on up.

307. The magnetic susceptibilities of metallic oxides, with special reference to those of chromium and manganese

Different workers report widely divergent results for tho magnetic susceptibilities of the transition metals. It has now been shown that, if the best values for the susceptibility are taken, the magnetic moment, as calculated from the Curie law, gives values which are of no theoretical significance, but application of Weiss's modification of this law to the oxides of chromium and manganese gives values for the magnetic moment which are in accord with theory and enable magnetic measurements to be used for the evaluation of the correct formulae of oxides. The formulae of the oxides of manganese are discussed, and the occurrence of quadrivalent chromium in a hydrated dioxide of that metal established. The magnetic susceptibility of tho various stages of decomposition of chromium trioxide has been measured, and it has been found that there is little change in the magnetic susceptibility with variation of composition in non-stoichciometric oxides. The Cr 2 0 3 non-stoichciometric oxide is ferromagnetic. Samples of chromic oxide prepared by different methods have slightly different susceptibility values. It is suggested that these differences are due to the presence of impurities and, in particular, to small amounts of chemisorbed gaseous elements, The adsorption of oxygen or of hydrogen at 440° on this oxide causes definite variation in tho susceptibility value. High-temperature evacuation likewise causes a considerable fall tn the susceptibility of chromic oxide. It is suggested that activated adsorption on oxides is connected with reduction of chemisorbed oxygen, and the use of magnetic measurements is recommended as a means of following surface chemical processes on oxides.