Enhanced Pauli paramagnetism

Where strong-correlation fluctuations are present in an itinerant-electron matrix, the magnetic susceptibility may be interpreted as a coexistence of Curie-Weiss and mass-enhanced Pauli paramagnetism. 

For these molecular metals, we still observe electronic correlations, whose presence is detected by an enhanced Pauli paramagnetism, and the analysis of the oscillator strength... 

Mixed valence compounds CeTjSij with T = Co, Ni show an enhanced Pauli paramagnetism with the fluctuation temperature around 150 K for Co and Ni which was established in the magnetic measurements in the temperature range of 1.6 to 600 K. The electrical resistivity measurements show that the compounds with T = Fe, Co and Ni do not become superconducting down to 18 mK and that the Fermi liquid behavior exists in the temperature range of 40 to 70 K (Ammar-guellat et al. 1987). 

The authors realized that the CEF field cannot be responsible for the observed low susceptibility. They proposed a model of non-bound f-electrons with enhanced Pauli paramagnetism. The sharp upturn at low temperatures could be due to impurities. It would certainly be interesting to reexamine these old results, in view of the progress which has been made in understanding mixed-valence systems. Furthermore, they are among the few available measurements which extended to high temperatures. X-ray photoemission measurements by Baer et al. (1978) confirm the existence of two valence states in CeN. Thus, the explanation of CeN being an intermediate-valence system is sustained. 

The large phase shifts t 2 give a large enhancement of the resistivity when transitional metals are dissolved in other metals. A survey for solid metals is given by Friedel (1956), and for solutions of Fe and Co in liquid germanium and tin by Dreirach et al (1972). The resonance will also enhance the electronic specific heat and the Pauli paramagnetism, but these quantities cannot be treated quantitatively without including correlation as shown in Chapter 3. 

We note that when moments do not appear an enhancement of the Pauli paramagnetism x is expected of the form... 

The superconducting (BEDT-TTF)2X are Pauli paramagnets in their normal states,but the a-salts with the same X have the strongly enhanced and temperature-dependent susceptibility, characteristic of a low-dimensional antiferromagnet. The magnitude of the susceptibility is exactly what one would expect for one unpaired electron per (BEDT-TTF)2 dimer An even... 

The x(T) curve for x = 0 is temperature-independent above 200 K, but it is enhanced relative to a conventional Pauli paramagnetism by at least two orders of magnitude,... 

The factor S was first obtained theoretically by Stoner (1938) in an attempt to rectify the poor agreement between the theoretical prediction of the Pauli susceptibility and the experimental values of the strongly paramagnetic alloys of transition metals. Attempts to clarify the microscopic origin of the enhancement factor came first from Izuyama et al. (1963) and Hubbard (1963). The dynamics of the electrons in the band is now completely described by the Hamiltonian ... 

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