Magnetic oxide surfaces

Corundum-type Magnetic Oxide Surfaces. The substrate hematite with the corundum-type crystal structure is an antiferromagnet below 963 K. In the corundum-type structure of hematite, pairs of ferric ions are in a row spaced by single vacant sites along the <111> direction. The positions of ferric ions in each pair are shifted slightly upward or downward in the <111> direction. We denote these lattice positions as up and down sites (Au and A ), respectively. 

Unalloyed steel can be directly oxidized by steam at temperatures over 750 °F (399 °C). Extensive cracks may occur, the steel surface may resemble tree bark, and magnetic oxide deposits are generated at the failure site. Intergranular oxidation may take place. In the thermal oxidation reaction, hydrogen is directly released as shown ... 

In spite of the development of physicochemical techniques for surface analysis, spectroscopic methods applicable to the study of bonding between adsorbed metal ion species and substrate are limited, especially those applicable to in situ measurement at interfaces between solid and aqueous phases (1,2). In previous papers, we showed that emission Mossbauer measurement is useful in clarifying the chemical bonding environment of dilute metal ions adsorbed on magnetic metal oxide surfaces (3,1 ) ... 

The results of Weiss field calculation on ferric ions at the surface metal ion sites are given in Figure 6 of ref 4, and the values for room temperature are shown in Figure 10. Since both ferric and pentavalent Sb ions can occupy octahedral or distorted octahedral sites with six ligand oxide ions and bulk hematite is considered to accommodate pentavalent Sb—119 ions in the metal ion sites (3 ), we can estimate STHF interactions on tetravalent Sn-119 ions at the surface metal ion sites of hematite. Using the magnetization of surface ferric ions at room temperature, the STHF magnetic fields on tetravalent Sn-119 ions at the surface sites are calculated to be... 

Theoretically, to produce 1000 cubic feet of hydrogen 30 inches barometric pressure and 40° F., ii6 5 lb. iron and 49 95 lb of steam are required however, in actice these figures are not closely approached because e magnetic oxide of iron formed tends to shield the stallic iron from the action of the steam indeed, the action may be regarded as merely a surface one. 

For adsorption studies the labeled polymer was dissolved in reagent grade solvent, the oxide surface added, and the sample was stirred magnetically for at least 2k hrs. (sometimes up to 3 days). The oxide with adsorbed polymer was separated from the unadsorbed polymer by gravity settling, or where necessary by low field centrifugation. The oxide together with adsorbed polymer was washed with fresh solvent until no ESR activity was detectable in the supernatant. The ESR spectrum was then taken of the polymer on the surface either in the presence of solvent, or after solvent removal as a function of temperature. 

Huang YC, Fowkes FM, Loyd TB (1991) Acidic and basic nature of ferric oxide surfaces. Adsorption, adhesion, zeta potential and dispersibility in magnetic inks for hard disks. In Mittal KL, Anderson HR (eds) Acid-Base-Interactions. VSP Utrecht, p 363... 

Alloys Borates Solid-state Chemistry Carbides Transition Metal Solid-state Chemistry Chalcogenides Solid-state Chemistry Diffraction Methods in Inorganic Chemistry Electronic Structure of Solids Fluorides Solid-state Chemistry Halides Solid-state Chemistry Intercalation Chemistry Ionic Conductors Magnetic Oxides Magnetism of Extended Arrays in Inorganic Solids Nitrides Transition Metal Solid-state Chemistry Noncrystalline Solids Oxide Catalysts in Solid-state Chemistry Oxides Solid-state Chemistry Quasicrystals Semiconductor Interfaces Solids Characterization by Powder Diffraction Solids Computer Modeling Superconductivity Surfaces. 

The last five years have witnessed a tremendous effort to better produce, characterise and study insulating oxide surfaces. Several reasons stem for the rapid development of this field. They are related to experimental considerations — a better control of the fabrication of surfaces, a more thorough use of advanced spectroscopic or structural tools — but also to a more accurate recognition of the technological importance of high quality oxide surfaces in catalysis, magnetic recording, as sensors or as constituents of artificial nano-materials. 

The HF method has been implemented on periodic systems [15], including bulk and surface crystalline materials. It has proved very useful in the description of magnetic insulators, but it has also successfully been used for describing surface properties of a large number of simple oxide surfaces. 

Oxides surfaces are finding continuous new applications in advanced technologies like in corrosion protection, coating for thermal applications, in catalysis as inert supports or directly as catalysts, in microelectronics for their dielectric properties films of magnetic oxides are integral components in magnetic recording devices and many microporous materials are based on oxides. For all these reasons there is a considerable effort to better characterize the surface and the interface of oxide materials [1,2]. 

The analysis of the electronic structure of Cr203(0001), as discussed so far, has been performed at 90 K. We note that upon increasing the temperature, the structure of the surface changes [ 107], and we have speculated that these changes are connected with changes in the magnetic structure of the surface. Oxide surface magnetism is a field that needs to be explored in the future. 

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