Magnetic properties of complex oxides Gd2SrM2O7 (M = Fe, Al)

Magnetic susceptibility of complex perovskite-like oxides Gd₂SrFe₂O₇ and Gd₂SrAl₂O₇ was studied. A sharp decrease in the magnetic characteristics of gadolinium ferrite as compared to gadolinium aluminate points to the presence of strong antiferromagnetic interactions between the iron ions.     

Electrical and Mechanical Properties of the High-Permittivity Ultra-High-Molecular-Weight Polyethylene-Based Composite Modified by Carbon Nanotubes

Technical Physics - A composite based on ultra-high-molecular-weight polyethylene (UHMWPE) added with 1 wt % of multiwalled carbon nanotubes (MWCNTs) with a high permittivity (ε = 4.5) and a...     

State of atoms of the transition group elements in dilute solid solutions based on LiMO2 (M = Sc, Ga, Al): II. Magnetic characteristics of nickel atoms in LiNi x Sc1 ? x O2 solid solutions

The state of nickel atoms in LiNi _x Sc_{1 − x} O₂ solid solutions was studied. The anomalous magnetic characteristics can be accounted for only by the presence of dilution-resistant clusters containing Ni(III) in two states: high- and low-spin. Original Russian Text ? A.A. Selyutin, N.P. Bobrysheva, N.V. Chezhina, A.V. Shchukarev, A.O. Kozin, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77, No. 10, pp. 1608–1612. For communication I, see [1].     

Synthesis and magnetic properties of two-dimensional vanadium(IV) oxide nanostructures on silica surface

Vanadium(IV) oxide nanolayers on silica surface were prepared for the first time. Samples characterized by different degrees of surface coverage by vanadium(IV)-oxygen groups were studied. Samples containing only vanadium(IV) ions and both vanadium(IV) and vanadium(V) ions were obtained. The size effect on the phase transition parameters was determined by studying magnetic properties of vanadium(IV) oxide nanolayers. The phase transition temperature ranges from 140 to 220 K, depending on surface concentration of vanadium(IV) ions and their environment.     

Geometric frustrations in magnetically diluted complex oxides Li<Emphasis Type="Italic">M</Emphasis>O<Subscript>2</Subscript> (<Emphasis Type="Italic">M</Emphasis> = Sc,Ga, 3<Emphasis Type="Italic">d</Emphasis> elements)

The effect of local environment of a transition-element atom on the properties of bulk ceramics has been investigated by the example of complex oxides LiMO₂ (M = Sc, Ga, Fe, Co, Ni). It is found that the anomalies in the magnetic properties of all systems studied are due to the presence of nanoclusters of transition-element atoms and the magnetic and geometric frustrations related to the nanocluster formation.     

Characterization of aluminum-carbon composites obtained via mechanical activation of aluminum and carbon nanotubes

The relaxation of structural defects of aluminum-multiwall carbon nanotubes (MWCNT) composite materials obtained via mechanical activation is studied in situ by X-ray diffraction using synchrotron radiation. Mechanically activated Al-MWCNT mixtures are annealed at temperatures of up to 600°C in an inert gas flow and X-ray diffraction patterns are simultaneously registered with a position-sensitive X-ray detector. It is demonstrated that mechanically activated samples of pure Al and composites with large-diameter MWCNTs (～20 nm) begin to experience the relaxation of defects accumulated during mechanical activation at temperatures as low as 100–150°C, while samples with small-diameter MWCNTs (～10 nm) exhibit thermal stability of structural defects up to 500°C.     

State of atoms of the transition group elements in dilute solid solutions based on LiMO2 (M = Sc, Ga, Al): III. State of iron and lithium atoms in the LiFe x Sc1−x O2 solid solutions

LiFe _x c_1?x O₂ solid solutions (0.005 < x < 0.10) were studied by the NMR and magnetic susceptibility methods. The anomalies of temperature and concentration dependences of magnetic susceptibility are accounted for by the contributions of single iron atoms and clusters containing iron, oxygen, and lithium atoms. According to the NMR spectroscopy data, lithium atoms also are in two states and enter the cluster composition.     

Magnetic properties of iron atoms in the perovskite-like oxides

Magnetic and structural characteristics of magnetically diluted complex oxides La_2?x A _x MO₄ (M is Fe; A is Sr, Ba) were studied. An essential dependence of magnetic susceptibility on the composition of dia- and paramagnetic components of the structure and also the tendency of heterovalent iron atoms to form clusters were found.