Ferromagnetic metal oxides

Other ferromagnetic metallic oxides are CoS2 and FeS (high-spin d6). In these also the moment appears close to the value for the free ion (Wilson 1972). 

Ferromagnetic metal oxide particles (magnetite) have been dispersed with a fluorinated surfactant [C8F 7S02N(C2H5)CH2C00K] in a fluorocarbon-type solvent to make magnetic fluids [65]. 

Nickel is a silver-white, lustrous, hard, malleable, ductile, ferromagnetic metal that is relatively resistant to corrosion and is a fair conductor of heat and electricity. Nickel is a ubiquitous trace metal that occurs in soil, water, air, and in the biosphere. The average content in the earth s crust is about 0.008%. Nickel ore deposits are accumulations of nickel sulfide minerals (mostly pentlandite) and laterites. Nickel exists in five major forms elemental nickel and its alloys inorganic, water-soluble compounds (e.g., nickel chloride, nickel sulfate, and nickel nitrate) inorganic, water-insoluble compounds (e.g., nickel carbonate, nickel sulfide, and nickel oxide) organic, water-insoluble compounds and nickel carbonyl Ni(CO). ... 

XPS measurements demonstrated that loaded Ni is predominantly located between the layeres of the catalyst and little remains on the external surface.15) For sensitivity reasons, a sample with 1 wt% Ni-loading was used. Comparison of the Ni2p3/2 peak intensity in the catalyst with that in a reference sample (which was also 1% Ni-loaded KNb03 with almost the same BET surface area as that of K4Nb6017) has shown that the surface concentration of Ni in the former is about 100 times less than that of the reference sampled EXAFS spectra for 1 wt% Ni-loaded samples both before and after the reduction procedure, as well as for Ni and NiO as standards, indicated that after reduction by H2 at 500°C for 2 b the loaded Ni was completely reduced to the metallic state.15) Even after reoxidation by 02 at 200°C for 1 h, most of the Ni remained metallic. (By XPS, the Ni, which remained on the external surface, was found to be in the oxidized form.) The formation of metallic nickel on a 0.1 wt% Ni-loaded catalyst was also confirmed by ESR measurements.7 The appearance of an intense resonance line after the reduction and reoxidation indicates the formation of ferromagnetic metallic nickel in the sample. 

The Kagome lattice structure clearly explains the non-symmetric nature of the band structure of the C0O2 layer. When the effect of the Kagome lattice becomes dominant, the bottom band, i.e., the flat band as shown in Fig, 3(a) will play a crucial role on the electronic state. Mielke [32] has shown that the flat band with the Coulomb interaction has the ferromagnetic ground state at around half filling. A prospective system for the ferromagnet will be dl transition metal oxides, i.e., the layered titanates with iso-structure of the cobalt oxides. 

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