Metallic character magnetic

As will be discussed later (Section 1.5), molecules containing no metallic elements are able to combine and form materials exhibiting metallic character, e.g., HMTSF-TCNQ, TTF-TCNQ, etc., or even lose any electrical resistance below a given temperature and thus become superconductors, e.g., (TMTSF)2C104. Metal-free molecules can also, in the solid state, show magnetic order, such as / -NPNN and /7-NC-C6F4-CNSSN, where in the absence of -electrons the magnetic properties are related to unpaired -electrons. 

PuP amongst compounds of metallic character, plutonium pnictides PuP, PuAs, PuSb are ferromagnetic. PuP has been studied not only by the magnetization technique but also by neutron diffraction specific heat and Powder polarized neutron... 

A ligand field model has been used for the interpretation of the magnetic behavior of the Mo(R2Dtc)4 complexes (485). Extended Hiickel calculations compare the electron-donating characteristics of the dithiocarbamate ligand to other 1,1-dithio chelates. This calculation concluded that (1) there is more metal character in the lowest unoccupied MO in the dithiocarbamate complexes, and (2) there is more ligand character in the lowest unoccupied MO in the dithioacid complexes (485). This seems to be in agreement with the electronic spectra. 

The sulfide ion stabilizes chromium in its lower oxidation states. Thus, both Ct2S3 and CrS exist, bnt a chromium(VI) trisulfide does not. Heating of Ct2S3 canses decomposition, leading to CrS by way of a number of phases of intermediate composition. Both Cr2Ss and CrS are semiconductors and exhibit magnetic ordering some of the other snlfides exhibit metallic character. 

In terms of both abundance in the Earth s crust (and on planetary surfaces) and numbers of species, most minerals are ionic and covalent in character, rather than metallic. Their magnetism, therefore, is appropriately described in terms of the magnetism of their cations and anions, rather than in terms of band magnetism of conduction electrons. Prominent exceptions are the Fe-Ni phases found in meteorites and that are relevant to planetary cores. Even in metallic minerals, however, the magnetism of the closed shell cation cores can, to a good first approximation, be treated independently from the conduction electron magnetism. 

Copper-63 NMR/NQR spectra for CuS, from 4.2K up to ambient temperatures, show two distinct lines based on the abrupt change in the spectrum at 55K. This is ascribed to a structural phase transition for both the powder and the oriented CuS. A more recent study of powdered samples at temperatures as low as 1.5K under a magnetic field of 6.5 T revealed more detail. An intense resonance with satellites was observed at all temperatures up to the ambient. This peak consisted of two resonance lines above 60K and four lines below 50K. The splittings observed correspond to crystal distortions below 55K. The central peaks with satellites were assigned to the metallic Cu(l) and Cu(2) in the crystal structure of CuS, for which spin-lattice relaxation times of 4 ms and 55 ms, respectively, were measured at 15K. The authors suggest that the anomalously short Ti for Cu(l) is indicative of the metallic character in the plane formed by Cu(l)-S bonds. 

In terms of electric, magnetic and mechanical properties, oxides exhibit a fairly wide range of behaviour. From an electronic point of view, they can be insulators, semiconductors or even show metallic character. They also... 

There are a few important consequences of this interaction, besides the magnetic quenching. While free Ni clusters have virtually no gap at the Fermi level, a typical sign of developing metallic character, carbonylated Ni clusters do have a gap of ca 1-2 eV, typical of semiconducting materials (Fig. 11). 

The first transition series or 3d-orbital series has a weak metallic character and less of atendancy for covalent bonding. This series also has strong oxidizing properties when in higher oxidation states. It forms many compounds with unpaired electrons, making it useful for catalysis and as magnetic materials. 

CNTs have a interesting feature of align their axis as an external field [52] (electrical [53-55] or magnetic [56, 57]) is applied. This property is applied, for example, for alignment during the synthesis [58] or to separate the CNTs according to the semiconducting or metallic character [59]. 

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