Electronic structure, magnetic ordering and X-ray magnetic circular dichroism in La1−x_{1-x}Prx_xCo2_2P2_2 phosphides

The electronic structure and magnetic ordering in La$_{1-x}$Pr$_x$Co$_2$P$_2$ ($x=$0, 0.25, and 1) phosphides have been studied theoretically using the fully relativistic spin-polarized Dirac linear muffin-tin orbital (LMTO) band-structure method. The X-ray absorption and X-ray magnetic circular dichroism spectra at the Co$L_{2,3}$ and Pr$M_{4,5}$ edges have been investigated theoretically within the framework of the LSDA+$U$ method. The core-hole effect in the final state as well as the effects of the electric quadrupole $E_2$ and magnetic dipole $M_1$ transitions have been investigated. Good agreement with experimental measurements has been found.Comment: 11 pages, 8 figure

Artificial drainage of peatlands: hydrological and hydrochemical process and wetland restoration

Peatlands have been subject to artificial drainage for centuries. This drainage has been in response to agricultural demand, forestry, horticultural and energy properties of peat and alleviation of flood risk. However, the are several environmental problems associated with drainage of peatlands. This paper describes the nature of these problems and examines the evidence for changes in hydrological and hydrochemical processes associated with these changes. Traditional black-box water balance approaches demonstrate little about wetland dynamics and therefore the science of catchment response to peat drainage is poorly understood. It is crucial that a more process-based approach be adopted within peatland ecosystems. The environmental problems associated with peat drainage have led, in part, to a recent reversal in attitudes to peatlands and we have seen a move towards wetland restoration. However, a detailed understanding of hydrological, hydrochemical and ecological process-interactions will be fundamental if we are to adequately restore degraded peatlands, preserve those that are still intact and understand the impacts of such management actions at the catchment scale

Magnetic Hyperfine Structure of Epitaxial Films of Nickel Ferrite

Comparative NGR study of the parameters of the magnetic hyperfine structure of epitaxial NiFe2O4 films grown on MgO single-crystal substrates of orientations of (100) and (111) by liquid phase epitaxy (LPE) and chemical transport reactions (CTR) is conducted. It is established that in the films obtained by the method of CTR, there is a significant number of ions of bivalent iron, which is in phase magnetite Fe2+Fe23+O4 . After heat treatment of these films in air at T = 1273 K, the magnetite becomes the Fe2O3 oxide. In the films of NiFe2O4, grown by the LPE method the divalent iron was not detected. As shown by calculations, the vector direction of the magnetization of films obtained by the method of LPE, lies in the film plane regardless of the orientation (100) or (111) MgO substrates. In films obtained by the CTR method, it forms with the substrate 41 - 450. Keywords: liquid phase epitaxy, chemical transport reactions, ferrite films, magnetic anisotropy, nuclear gamma resonance.</p

Synthesis and Properties of Mesoporous Maghemite

Mesoporous maghemite (γ -Fe₂O₃), obtained by thermal decomposition of iron citrate xerogel hydrate, was investigated by X-ray diffraction, scanning electron microscopy, the Mössbauer and impedance spectroscopies and low temperature nitrogen adsorption. The influence of precursor molar concentration on the material morphology, crystalline and magnetic microstructures and electric conductivity was studied. Obtained results open up the possibility for synthesis of ultrafine γ -Fe₂O₃ with controlled structural and morphological characteristics

Synthesis and Properties of Mesoporous Maghemite

Mesoporous maghemite (γ -Fe₂O₃), obtained by thermal decomposition of iron citrate xerogel hydrate, was investigated by X-ray diffraction, scanning electron microscopy, the Mössbauer and impedance spectroscopies and low temperature nitrogen adsorption. The influence of precursor molar concentration on the material morphology, crystalline and magnetic microstructures and electric conductivity was studied. Obtained results open up the possibility for synthesis of ultrafine γ -Fe₂O₃ with controlled structural and morphological characteristics

Electronic structure and X-ray magnetic circular dichroism in the MAX phases T_2AlC (T = Ti and Cr) from first principles

We study the electronic and magnetic properties of T_2AlC (T = Ti and Cr) compounds in the density-functional theory using the generalized gradient approximation (GGA) with consideration of strong Coulomb correlations (GGA+U) in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital (LMTO) band-structure method. The X-ray absorption spectra and X-ray magnetic circular dichroism (XMCD) at the Cr L_(2,3) and Cr, Ti, and C K edges were investigated theoretically. The calculated results are in good agreement with experimental data. The effect of the electric quadrupole E_2 and magnetic dipole M_1 transitions at the Cr K edge has been investigated

Influence of Structural Defects in Epitaxial Ferrite-Garnet Films on their Magnetic Properties

The study of defects observed in substrates with gadolinium gallium garnet (GGG) with orientations (110), (100) and (111) and in epitaxial films grown of iron-yttrium garnet (YIG) were investigation. It is shown that the line width ferromagnetic resonance strongly depends on the presence of defects in YIG films. It was established that the highest quality and minimal magnetic losses have YIG films with a thickness of 2...8 mm grown on GGG defect-free substrates with orientation (111), which were grinding and polishing the surface to 14 grade purity. Keywords: ferrite-garnet film, structural defects, ferromagnetic resonance