A mass-extended 't Hooft-Nobbenhuis complex transformations and their consequences

We have extended the 't Hooft-Nobbenhuis complex transformations to include mass. Under these new transformations, Schrodinger, Dirac, Klein-Gordon and Einstein general relativity equations are invariant. The non invariance of the cosmological constant in Einstein field equations dictates it to vanish thus solving the longstanding cosmological constant problem.Comment: 6 LateX pages, no figure

Fluorinated perovskite as magnetic spin-polarised semiconductor

Much work has been done on cation substitution of manganese perovskites, but less on anion substitution. Recently there have been reports on fluorination of these compounds, generally leading to double perovskite structures. This work explores the effect of fluorine substitution on the magnetic and electrical properties of the perovskite cubic strontium manganite using first principles DFT calculations. Results on fluorine-doped strontium manganite with one or two fluoride ions surrounding each iron are presented. The ground state of Sr2Mn2O5F is found to be a small band gap spin-biased semiconductor. This is the first proposal that a fluorinated manganite could be a ferromagnetic spin-polarised semiconductor

On the generalized continuity equation

A generalized continuity equation extending the ordinary continuity equation has been found using quanternions. It is shown to be compatible with Dirac, Schrodinger, Klein-Gordon and diffusion equations. This generalized equation is Lorentz invariant. The transport properties of electrons are found to be governed by Schrodinger-like equation and not by the diffusion equation.Comment: 9 Latex pages, no figure

Structural, 57 Fe Mössbauer and XPS studies of mechanosynthesized nanocrystalline Nd0.33Eu0.67Fe1-xCrxO3 particles

We report on the structure and surface composition of Nd0.33Eu0.67Fe1-xCrxO3 (x = 0.0, 0.3, 0.5, 0.7, 0.9 and 1.0) nanoparticles (∼30 nm) mechanosynthesized at temperatures that are ∼ 470– 700 °C lower than those at which the pure and doped pristine materials conventionally form. XRD Rietveld and FT-IR analyses show that with increasing x the lattice parameters decrease and the bond lengths and angles vary in a way that reduces crystalline distortion. Whilst the majority of the Eu3+/Nd3+ and Fe3+/Cr3+ cations occupy the normal perovskite-related A- and B-sites, respectively, ∼ 5% of them exchange sites. 57Fe Mössbauer spectroscopy confirms the presence of these antisites and reveals a superparamagnetic behaviour at 298 K that enhances with increasing x. XPS measurement reveals a complex surface composition of the nanoparticles with traces of Eu2O3, Nd2O3, Cr2O3 and Fe2O3 as well as partial O2--deficiency

The hyperfine properties of a hydrogenated Fe/V superlattice

: We study the effect of hydrogen on the electronic, magnetic and hyperfine structures of an iron-vanadium superlattice consisting of three Fe monolayers and nine V monolayers. The contact charge density ({\rho}), the contact hyperfine field (Bhf) and the electronic field gradient (EFG) at the Fe sites for different H locations and H fillings are calculated using the first principle full-potential linear-augmented-plane-wave (FP-LAPW) method . It is found that sizeable changes in the hyperfine properties are obtained only when H is in the interface region.Comment: 6 pages, 2 figures, 3 tables, ICAME 2011 conference (Kobe, Japan

Iron(III) as a defect in diantimony tetroxide

Defect structures for Fe(III) in both alpha- and beta-diantimony tetroxide are explored using computer modelling techniques. A new favourable interstitial position for Fe(III) is identified, but the most energetically favourable defect reaction incorporating Fe(III) in diantimony tetroxide was found to be that in which the transition metal ion replaced an Sb(III) ion. The most favourable intrinsic defect in diantimony tetroxide is found to be an oxide ion Frenkel defect. This is considerably more favourable for the alpha form due to the asymmetric structure of this form. Incorporation of iron close to such a defect makes substitution on the Sb(III) site more favourable for the beta form

Defect clusters in titanium-substituted spinel-related lithium ferrite

The cation distribution in spinel-related titanium-substituted lithium ferrite, Li0.5+0.5xFe2.5−1.5xTixO4 has been explored using interatomic potential and ab initio calculations. The results suggest that the cation distribution with Ti4+ substituting for Fe3+ on octahedral B sites and excess Li+ substituting for Fe3+ on tetrahedral A sites is stabilised by the formation of clusters of two octahedrally coordinated Ti4+ ions and one tetrahedrally coordinated Li+ ion linked through a common oxygen

The influence of mechanical milling and subsequent calcination on the formation of lithium ferrites

The influence of ball milling and subsequent calcination of a 2.5:1 molar mixture of alpha-Fe2O3 and Li2CO3 on the formation of lithium ferrites has been investigated. Premilling was found to considerably lower the temperature at which the lithium ferrites LiFeO2 and LiFe5O8 are formed. A beta-to-alpha-phase transition in LiFe5O8 was found to take place on cooling from ca. 1000degreesC depending on the milling history and cooling regime. (C) 2002 Elsevier Science (USA)