Ferromagnetic enhanced

Now for ordinary metals such as the alkali metals at high density, the function f(Q) decreases monotonically with Q, behaving like the Lind-hard dielectric function for the nonuniform susceptibility of a free electron gas (see, e.g., Ashcroft and Mermin, 1976). Thus, the largest enhancement occurs for Q = 0. This is sometimes referred to as ferromagnetic enhancement—the greatest enhancement occurs for the uniform susceptibility. For sufficiently large a, theory predicts that such a system should be a metallic ferromagnet at low temperatures. 

While mononuclear octahedral Ni11 complexes often show relatively broad signals, nuclear relaxation enhancement and sharp signals may be observed in related dimer species 350,351 This has been taken advantage of for a detailed NMR investigation of a series of weakly ferromagnetically spin-coupled dinuclear octahedral Ni11 centers.352... 

There are a number of defects that could give rise to magnetic properties alone or interact with magnetic impurities to enhance magnetic behavior. In ZnO-based films such as Ziij vCuvO, ferromagnetism is believed to arise with Zn2 or Zn, interstitials. 

Note that in the latter case the relaxation rate enhancement also depends on the sign of J, i.e., on the coupling being antiferromagnetic (J > 0) or ferromagnetic (J < 0). 

The first chemical transformations carried out with Cjq were reductions. After the pronounced electrophilicity of the fullerenes was recognized, electron transfer reactions with electropositive metals, organometallic compounds, strong organic donor molecules as well as electrochemical and photochemical reductions have been used to prepare fulleride salts respectively fulleride anions. Functionalized fulleride anions and salts have been mostly prepared by reactions with carbanions or by removing the proton from hydrofullerenes. Some of these systems, either functionalized or derived from pristine Cjq, exhibit extraordinary solid-state properties such as superconductivity and molecular ferromagnetism. Fullerides are promising candidates for nonlinear optical materials and may be used for enhanced photoluminescence material. 

Mito M, Kawae T, Takeda K, Takagi S, Matsushita Y, Deguchi H, Rawson JM, Palacio F (2001) Pressure-induced enhancement of the transition temperature of a genuine organic weak-ferromagnet up to 65 K. Polyhedron 20 1509-1512... 

To summarize, we again want to make a sharp distinction between the enhancement in nearly ferromagnetic metals like Ni3Al, where the Stoner enhancement factor can increase x without limit but not dx/dT or y, and the enhancement in nearly antiferromagnetic metals to be discussed in Chapter 4, where x> V and dx/dT are all enhanced. In the former case, all models involve either a non-integral number of electrons in the band or degenerate orbitals. In the latter, two electrons on the same atom necessarily have antiparallel spins. 

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