Magnetic susceptibility paramagnetic contribution

The disappearance of the paramagnetism of palladium-silver alloys (rich in Pd) when the ratio (H + Ag)/Pd = 0.6 (24) illustrates that the effect of both these alloying" elements in palladium is additive and each one contributes essentially in the same way to the change of magnetic susceptibility of palladium. 

The temperature dependence of the molar magnetic susceptibility (x) of an assembly of paramagnetic spins without interaction is characterized by the Curie behavior with x = C/T where C = /Vy2( 2.S (.S + l)/3k. It is a very common situation in the organometallic chemistry of radical species when the spin density is essentially localized on the metal atom. Since, in most cases, this atom is surrounded by various innocent ligands, intermolecular interactions are very weak and in most cases are reflected by a small contribution described by a Curie-Weiss behavior, with x = C/(T 0) where 0 is the Curie-Weiss temperature. A positive value for 0 reflects ferromagnetic interactions while a negative value — the most common situation — reflects an antiferromagnetic interaction. 

Direct application of Ax for the quantitative evaluation of aromaticity is, however, not practicable since its magnitude is not determined by ring currents only. Quite substantial effects may be played by a local contribution by the 7r-bond anisotropy and the anisotropy of CC and CH (r-bond magnetic susceptibilities as well as by the anisotropy due to local paramagnetic currents (for more detail, see, e.g., 66MI1). 

It is useful to consider typical values of different contributions to the magnetic susceptibility. One important component is the Curie susceptibility arising from isolated (i.e., noninteracting) paramagnetic ions with g-factor g and spin S which is given by ... 

Another additive term in the magnetic susceptibility arises from the temperature-independent core diamagnetism of all the ions in a solid. For YBa2Cu307 the core diamagnetism is approximately -2 x 10 7 based on a calculation using Pascal s constants (9). This small negative contribution serves to reduce the total susceptibility. A third possible contribution arises from Van Vleck paramagnetism (10) caused by excited states in the atoms of the... 

When discussing the electrical conductivity of metals, we described them in terms of ionic cores and delocalised valence electrons. The core electrons contribute a diamagnetic term to the magnetic susceptibility, but the valence electrons can give rise to paramagnetism or one of the cooperative effects we have described. 

In suitable systems the g-value can be measured with great accuracy. Also, the ESR experiment is such that each paramagnetic ion contributes separately to the spectrum, and in principle the contributions can be obtained separately. This is in contrast to the magnetic susceptibility, where the experiment reflects only the average of the contributions of individual ions in a crystal. 

The magnetic susceptibility is also derived from the electron density. There are two contributions (19) the Pauli paramagnetism and the Landau diamagnetism. The former is given by... 

The third-rank diamagnetic and paramagnetic contributions to electric field dependent magnetic susceptibility and nuclear magnetic shielding, to first order in... 

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