Polymer assisted spherical FeNi nanoparticles were prepared via wet chemical method using hydrazine as a reducing agent and polymers (PVP and PEG) as reducing and stabilizing agent. Structural studies performed using XRD and TEM shows uniform dispersion of fine FeNi nanocrystallites in nanocomposite particles. The size and thermal stability of FeNi nanoparticles prepared under same reaction condition was found to be dependent on the type and the molecular weight of the polymer used. However, the magnetic properties of nanocomposite particles were not influenced by the polymers. The study highlights subtle differences in using polymers during the synthesis of alloyed nanocomposite particles.

Iron phosphate (Fe2O3-P2O5) glasses with a high Fe2O3 content are particularly interesting in that they exhibit short range antiferromagnetic (speromagnetic) ordering at low temperatures. Neutron scattering techniques have been employed to investigate the atomic and magnetic structure and dynamics of four iron phosphate glasses, as a function of their nominal composition between 30 and 44 mol% Fe2O3, and the data are compared with earlier structural models in which the Fe3+ cations are either tetrahedrally or 6-fold co-ordinated by oxygen. Fe2+ cations are also found to be present in 6-fold (trigonal-prismatic and/or octahedral) co-ordination. Neutron magnetic diffraction experiments yield information concerning the Fe Fe distances and confirm the speromagnetic nature of the magnetic ordering, whilst a measurement of the magnetic inelastic scattering from vitreous 40Fe(2)O(3)center dot 60P(2)O(5) reveals the presence of dispersive magnetic excitations centred on the first magnetic diffraction peak at 0.82 angstrom(-1). It is concluded that all four glasses have structures that are much more complicated than the above models would suggest and include Fe3+ cations in both tetrahedral and octahedral co-ordination. A comparison with the structure of the corresponding crystalline phases suggests that the glasses are nanoheterogeneous, with FePO4-like regions (alternating Feempty set(4)(-) and Pempty set(4)(+) corner sharing tetrahedra) and those having a more typical phosphate chain structure incorporating Fe2+/Fe3+ network modifying cations.

Alloyed spherical FeNi-polymer nanocomposites were prepared via wet chemical method using hydrazine as a reducing agent and polymers (PVP and PEG) as reducing and stabilizing agent. Structural studies performed using XRD and TEM shows uniform dispersion of fine FeNi nanocrystallites in nanocomposite particles. The size and thermal stability of FeNi-polymer nanocomposite particles prepared under same reaction condition was found to be dependent on the type and the molecular weight of the polymer used. However, the magnetic properties of nanocomposite particles were not influenced by the polymers. The study highlights subtle differences in using polymers during the synthesis of alloyed nanocomposite particles.

Structural features and properties of a series of hafnium iron phosphate glasses have been investigated by Mössbauer spectroscopy and X-ray diffraction. Mössbauer spectra indicate that all of the glasses contain both Fe(II) and Fe(III) ions. The isomer shift values obtained from the Mössbauer fits show that both Fe(II) and Fe(III) ions are in octahedral or distorted octahedral coordination. The crystalline HfP2O7 phase was detected in all the samples by powder X-ray diffraction but this did not degrade the chemical durability of the glasses as the dissolution rates of the glasses are comparable to that of base iron phosphate glass.

Iron phosphate (Fe2O3-P2O5) glasses with a high Fe2O3 content are particularly interesting in that they exhibit short range antiferromagnetic (speromagnetic) ordering at low temperatures. Neutron diffraction techniques have been employed to investigate the atomic structure of iron phosphate glasses, as a function of composition between 30 and 44 mol% Fe2O3, and the data are compared with two structural models in which the Fe atoms are either tetrahedrally or 6-fold coordinated by oxygen. It is concluded that the structure is much more complicated than either of these models would suggest and that it includes Fe3+ ions in both tetrahedral and octahedral coordination. Fe2+ ions are also present in octahedral, and possibly 5-fold, coordination.

Accurate normalisation of high energy x-ray scattering data may be accomplished when the composition of the sample is known and the experimental corrections are either negligible or have been rigorously applied. However, for samples with unknown compositions, a priori normalisation is impossible. For binary rare earth phosphate glasses we demonstrate an iterative method for determining both the appropriate normalisation as well as determining the ratio of rare earth to glass former. The isotropic scattering is compared for several estimated compositions and fitted to the measured data over different Q-ranges. For high energy x-ray data (E=115keV) where the attenuation and multiple scattering corrections are very small the sample composition is insensitive to the Q-range used. We demonstrate this method for a rare earth phosphate glass sample and compare the results with established methods of atomic composition determination. The accuracy and applicability of the method is briefly discussed.

Exchange-coupled magnetic nanocomposite powders were obtained by mechanically milling ferromagnetic (FM)-antiferromagnetic (AFM) powders. A shift in the field-cooled (FC) hysteresis loop and the coercivity enhancement of the FM phase ensuing from exchange bias anisotropy was observed. The blocking temperature (TB) in all composites was found to be much lower than the Neel temperature (T-N) of the AFM phases. A model based on Preisach hysteresis was used to calculate the interfacial energy between FM and AFM particles. The calculated interfacial energies were highest for FM-CoO and lowest for FM-CuO composites. These values are in good agreement with those reported for polycrystalline AFM thin films.

The local structures around rare-earth ions in rare-earth ultraphosphate glasses (nominally 15RE(2)O(3)-85P(2)O(5), mol%, RE = Nd, Sm, Gd, Ho, and Er) and metaphosphate glasses (nominally 25RE(2)O(3)-75P(2)O(5), mol%, RE = Nd, Gd, and Er) have been studied by extended X-ray absorption fine structure spectroscopy (EXAFS) at the respective rare-earth L-III edges. The RE-O distance decreases with increasing atomic number of the rare-earth ion for both ultra and metaphosphate glasses. On average, RE-O distances for metaphosphate glasses are shorter than those for ultraphosphate glasses of comparable compositions. There are 7-8 oxygen nearest neighbors in the first co-ordination sphere around rare-earth ions in ultraphosphate glasses and similar to 6 oxygens in the first co-ordination sphere around rare-earth ions in metaphosphate glasses. There is no systematic dependence of the RE-O co-ordination number on the atomic number of the rare-earth ions in either compositional series. The second co-ordination shell around rare-earth ions in ultraphosphate glasses consists of phosphorus ions for all but the samarium ultraphosphate glass, with a RE-P distance between 3.53 and 3.85 angstrom and co-ordination numbers between 3 and 5. No RE-RE correlations were found within a distance of 4.5 angstrom. (c) 2005 Elsevier B.V. All rights reserved.

The phenomenon of spin freezing at low temperatures in iron-containing oxide glasses resulting from antiferromagnetic interactions has been previously reported for several oxide glass systems. The temperature dependence of the DC magnetic susceptibility has been measured with a SQUID magnetometer for a series of four iron oxide–phosphorus pentoxide glasses, containing between 30 and 44mol% Fe2O3, and prepared so as to have an Fe3+ fraction of ∼0.8. Well defined cusps are observed in the susceptibilities at temperatures between 5K and 8K for the four samples, cooled in zero field and measured at 0.025T. As for classical metallic spin glass alloys, the susceptibilities measured after cooling from high temperature in this field are almost constant below the cusp temperatures, corresponding to spins freezing into a complicated configuration. Similar measurements at 0.5T also demonstrate the freezing transition but the cusps in the susceptibility after zero-field cooling are broadened. The distribution and environments of iron ions within the samples are discussed in the light of the temperature-dependent magnetic structure factors and spin correlation functions, observed in neutron diffraction experiments on the same samples, along with the nuclear real space total correlation functions.

Intermetallic compounds of NdMn6-xFeSn6 (0 less than or equal to x less than or equal to 2.0) were studied by means of x-ray and neutron diffraction techniques and SQUID magnetic measurements in the temperature range of 30-400 K. The substitution of iron for manganese leads to a phase transition whereby NdMn6Sn6 with the HoFe6Sn6 structure (space group Immm) changes to TbFe6Sn6 (space group Cmcm) for NdMn6-xFexSn6 with x greater than or equal to 0.5. The iron atoms prefer to occupy the 8g sites at iron content x < 2.0 due to the longest Mn/Fe-Sn bond distance. The Curie temperature (T-C) increases from x = 0 to 1.5 and then decreases for the larger iron content. The magnetic moment of the iron sublattice couples ferromagnetically with the manganese and neodymium moments for the x < 2.0 samples. Spin reorientation is observed in samples with iron content up to 1.5, and the spin reorientation temperature (T-S) increases with increasing iron content. Except for NdMn4Fe2Sn6, the easy direction of magnetization for all samples is parallel and perpendicular to the (bc) plane of the unit cell at 300 and 30 K, respectively. The easy direction of magnetization for NdMn4Fe2Sn6 is parallel to the a-axis in the entire temperature range mentioned above, as a result of the anisotropic contraction of the unit cell along the (bc) plane.

Glass forming and crystallization characteristics, atomic structure, and redox equilibria in iron phosphate glasses containing varying amounts of a common waste component such as UO2, Cs2O, Bi2O3, SrO, Na2O, and MoO3 have been investigated using differential thermal analysis (DTA), Mossbauer spectroscopy, Fe-K edge X-ray absorption spectroscopy (XAS), Raman spectroscopy, and neutron and high energy X-ray scattering. None of the waste components adversely affect the redox equilibria attained during melting in air. Raman spectra, Mossbauer hyperfine parameters, and Fe-K edge XAS data indicate that neither the near neighbor environment of the iron ions nor the phosphorus-oxygen network is appreciably altered by the waste components. However, the incorporation of waste elements into the iron phosphate glass matrix is evident in the high energy X-ray and neutron scattering data.

The coordination environments of Pt impurities in a ternary K‐aluminophosphate (KAP) glass and commercial K,Mg‐aluminophosphate (KMAP) laser glasses have been investigated by Pt LIII‐edge X‐ray absorption fine structure (XAFS) spectroscopy. Pt valence in the KAP glass depends on the melt preparation atmosphere. Pt4+ ions form in melts that are bubbled with oxygen, whereas metallic Pt particles form when these same samples are remelted in air. Residual chlorine in KMAP glasses has an effect on Pt bonding. In chlorine‐free samples, Pt4+ ions are coordinated with ∼5.4 (8) oxygen atoms with an average distance of 2.02 (1) Å. For glasses with low chlorine contents (<200 ppm Cl), the Pt4+ ions have both O and Cl atoms in the first coordination shell. As the Cl concentration increases, the number of O nearest neighbors decreases and for Cl:Pt > 5, only Cl nearest neighbors are observed. Pt4+ ions in these latter glasses are coordinated by ∼5.5 (8) Cl atoms at an average distance of 2.27 (2) Å.