Susceptibility conduction electron

Unlike traditional surface science techniques (e.g., XPS, AES, and SIMS), EXAFS experiments do not routinely require ultrahigh vacuum equipment or electron- and ion-beam sources. Ultrahigh vacuum treatments and particle bombardment may alter the properties of the material under investigation. This is particularly important for accurate valence state determinations of transition metal elements that are susceptible to electron- and ion-beam reactions. Nevertheless, it is always more convenient to conduct experiments in one s own laboratory than at a Synchrotron radiation focility, which is therefore a significant drawback to the EXAFS technique. These focilities seldom provide timely access to beam lines for experimentation of a proprietary nature, and the logistical problems can be overwhelming. 

ESR can detect unpaired electrons. Therefore, the measurement has been often used for the studies of radicals. It is also useful to study metallic or semiconducting materials since unpaired electrons play an important role in electric conduction. The information from ESR measurements is the spin susceptibility, the spin relaxation time and other electronic states of a sample. It has been well known that the spin susceptibility of the conduction electrons in metallic or semimetallic samples does not depend on temperature (so called Pauli susceptibility), while that of the localised electrons is dependent on temperature as described by Curie law. 

It can be shown that the conduction electron net spin susceptibility is proportional to the temperature coefficient of the electronic heat capacity [cf. Eq. (4.42)] and, for free electrons in a single band, having the Fermi energy much lower than any band gap, is given by... 

Some metals are diamagnetic because the conduction electron spin susceptibility is smaller than the induced diamagnetic susceptibility component. On the other hand, various rare earth metals display very strong paramagnetism because of unpaired / electrons that remain associated with individual atoms rather than entering into energy bands. 

With this understanding, it is clear that in a given conduction 0 covalent transformation, a decrease or increase in the number of conduction electrons is an essential feature that should be observable in the transport properties. Assuming that the band structure of TiNi consists of a single positive band, a decrease in the number of conduction (free) electrons in the course of Ms —> As is equivalent to an increase in the number of hole carriers as seen in (c). Consequently, the positive Hall coefficient should decrease and is so observed in (b). Because holes contribute to Pauli paramagnetic susceptibility in precisely the same manner [42] as electrons, the paramagnetic susceptibility, %, is expected to rise and is so observed in (d). An increase in the hole carrier, Nh, would result in an increase in the conductivity (lowering in the resistivity) as... 

ESR spectra of the LB film of TMTTF-C18TCNQ show a single line without structures, which together with the observed g value indicates that there is strong coupling between TMTTF radical spins and TCNQ radical spins [59] as in the TTF-TCNQ crystal [60]. The temperature dependence of the spin susceptibility of the film suggests the presence of spin species due to conduction electrons. 

Fig. 2. Temperature dependence of the magnetic susceptibility x (right scale) and of the field for Pd NMR at fixed Larmor frequency Bo (left scale) for palladium. Similar to Fig. la, the NMR field shift and the susceptibility are proportional. Both are (mainly) caused by the Pauli-type paramagnetism of the d-like conduction electrons. (The temperature dependence is not predicted by the simple free-electron description of the susceptibility in metals.) [Reproduced with permission from Seitchik et al. (16). Copyright 1964 American Physical Society.]...

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