Cobalt ferromagnet

Cobalt is a bluish silvery metal, exhibits ferromagnetism, and can exist in more than one crystal form it is used in alloys for special purposes. Chemically it is somewhat similar to iron when heated in air it gives the oxides C03O4 and CoO, but it is less readily attacked by dilute acids. With halogens, the cobalt(II) halides are formed, except that with fluorine the (III) fluoride, C0F3, is obtained. 

Nickel is silvery white and takes on a high polish. It is hard, malleable, ductile, somewhat ferromagnetic, and a fair conductor of heat and electricity. It belongs to the iron-cobalt group of metals and is chiefly valuable for the alloys it forms. 

LCo(H20)6] ion, and bidentate /V-donor ligands such as cn, bipy and phen form octahedral cationic complexes [Co(L-L)3] , which are much more stable to oxidation than is the hexaammine [Co(NH3)6l . Acac yields the orange [Co(acac)2(H20)2] which has the tram octahedral structure and can be dehydrated to [Co(acac)2l which attains octahedral coordination by forming the tetrameric species shown in Fig. 26.3. This is comparable with the trimeric [Ni(acac>2]3 (p. 1157), like which it shows evidence of weak ferromagnetic interactions at very low temperatures. fCo(edta)(H20)] is ostensibly analogous to the 7-coordinate Mn and complexes with the same stoichiometry, but in fact the cobalt is only 6-coordinate, 1 of the oxygen atoms of the cdta being too far away from the cobalt (272 compared to 223 pm for the other edta donor atoms) to be considered as coordinated. 

Nickel is ferromagnetic, but less markedly so that either iron or cobalt and its Curie point (375°C) is also lower. 

The values for the atomic saturation magnetization at the absolute zero, ferromagnetic metals iron, cobalt, and nickel are 2.22, 1.71, and 0.61 Bohr magnetons per atom, respectively.9 These numbers are the average numbers of unpaired electron spins in the metals (the approximation of the g factor to 2 found in gyromagnetic experiments shows that the orbital moment is nearly completely quenched, as in complex ions containing the transition elements). 

Nickel is a malleable, ductile, tenacious, slightly magnetic, silvery white metal, which conducts heat and electricity fairly well. It is ferromagnetic at ordinary temperatures but becomes paramagnetic at elevated temperatures. Nickel is closely related in chemical properties to iron and cobalt. While sulphidic sources of nickel account for the world s major nickel supplies, it may be pointed out that lateritic nickel deposits (which essentially constitute an oxidic source of the metal) are more extensive than the sulphidic sources. 

In their demagnetized states, ferromagnetic metals, such as iron, cobalt, and nickel, consist of randomly magnetized domains separated by well-defined... 

The Russell group has applied the template synthesis approach to nanoporous films generated from UV-treated PS-fo-PMMA copolymers [43, 147,233,235,241], which were pre-aligned perpendicular to the substrate by an electric field. Through direct current electrodeposition, they fabricated high-density vertical arrays of ferromagnetic cobalt nanowires (Fig. 10a) [43]. Through subsequent work, they also demonstrated the successful replication... 

The spinel ferrites were fabricated by solid state reaction technique. Cobalt and Zinc ferrites CoxZnyFe204,(x=0.7,0.3,0.4,0.2 and y=0.3,0.7,0.6,0.8) were prepared by solid state reaction technique. The crystalline structure of the sample was investigated by X-ray diffraction(XRD). All samples show cubic spinel structure. The lattice parameter decreases with increasing cobalt content. Magnetic properties shows that the prepared sample exhibit ferromagnetic behaviour at room temperature. The saturation magnetization increases with increasing cobalt content. Curie temperature... 

Spectra of four supposedly identical catalysts containing cobalt supported on an activated carbon are shown in Fig. 28. The spectra show that the two good catalysts, B-1 and B-2, contained the cobalt mostly as CoO the poor catalysts, A-1 and A-2, contained the cobalt in the metallic form. This was supported by ferromagnetic comparisons of the... 

Cobalt-based catalysts are effective in the ethanol reformation to hydrogen. Many oxides have been used to prepare supported cobalt catalysts of low cobalt content (circa 1 wt%) by impregnation from a solution of Co2(CO)8 catalysts were used in the ethanol reformation as prepared [156]. The performance of the catalysts in the steam reforming of ethanol was related with the presence, under reaction conditions, of metallic (ferromagnetic) cobalt particles and oxidized cobalt species. An easy exchange between small metallic cobalt particles and oxidized cobalt species was found. Comparison of Co/ZnO catalysts prepared from Co2(CO)8 or from nitrate precursor indicated that the catalyst prepared from the carbonyl precursor was highly stable and more selective for the production of CO-free hydrogen... 

Aristov VY, Molodtsova OV, Ossipyan YA, Doyle BP, Nannarone S, Knupfer M (2009) Ferromagnetic cobalt and iron top contacts on an organic semiconductor evidence for... 

For a very few metals, however, the unpaired electrons in the conduction band can lead to ferromagnetism. In the whole of the Periodic Table, only iron, cobalt, nickel, and a few of the lanthanides (Gd, Tb) possess this property. So, what is so special about these elements that confers this uniqueness on them It is not their crystal structure they each have different structures and the structures are similar to those of other non-ferromagnetic metals. Iron, cobalt, and nickel, however, all have a nearly full, narrow 3c/band. 

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