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Mn, Co and Ni substituted Fe3.34Ge2 hexagonal germanides were investigated through structural, Mossbauer and magnetic studies. Fe was observed to enter exclusively 2a and 2d sites of the defective structure, while vacancies only occupy the 2d site in the congruent composition. The Ge atoms were found to be slightly displaced from 2c site of the B8(sub 2) structure towards an adjacent vacancy in a 2d site. Mn and Ni exclusively enter 2a and 2d site, respectively, while Co enters both sites with a preference for 2d.

The magnetic structure and magnetic excitations in nanocrystalline Tb is investigated by neutron diffraction and neutron spectroscopy. The origins of this excitation are discussed with particular reference to the magnetic modes at the zone center for single-crystal Tb.

The nonmagnetic doping effect of a TbB50-type compound TbB44Si2 is explored. The critical field Hc is not affected by the magnetic dilution of up to 50 percent and the transition in the TbB50-tye compounds is found to be of dimeric nature.

High incident energy inelastic neutron scattering, magnetization and x-ray powder diffraction measurements are used for examining the effects of diluting Gd with Y on the magnetic properties of the giant magnetocaloric effect material Gd5Si2Ge2. Gd4YSi1.9Ge2.1 orders ferromagnetically at 149 K with an effective paramagnetic moment of 7.87 muB and hence its ordering temperature is about half that of Gd5Si2Ge2.

The temperature dependence of the magnetic structure of Er90Pr10, Er80Pr20 and Er60Pr40 alloys is examined. A ferromagnetic phase and modulated structure components coexist in Er90Pr10 alloy with increasing temperature up to 35 K whereas a single ferromagnetic phase with moments parallel to the c-axis is observed from low temperatures up to the Curie point at 35 K for Er60Pr40

The magnetic structure at 15 K of LaFe(sub 10.8)Al(sub 2.2) and its ternary nitride LaFe(sub 10.8)Al(sub 2.2)N(sub 3) are determined by high resolution time-of-flight neutron powder diffraction. Magnetism in these materials is determined by clusters formed by a central Fe atom surrounded by Fe atoms with icosahedral symmetry.

Powder neutron diffraction at 1.5K has been used to investigate the crystal and magnetic structure, whilst the Singular Point Detection (SPD) technique has been used to measure the temperature and composition dependence of the magnetic anisotropy of [Fe.sub.60][Ga.sub.40-x][As.sub.x] (x = 6, 23) and Fe[Ga.sub.23][Sb.sub.17]. The compounds [Fe.sub.60][Ga.sub.17][As.sub.23] and Fe[Ga.sub.23][Sb.sub.17] are isotypic with [Ni.sub.2]In ([P.sub.63]/mmc) and [Fe.sub.60][Ga.sub.34][As.sub.6] is a complex modification of this with a doubling of the lattice constant a of the parent [Ni.sub.2]In subcell. The neutron data show that the magnetic structures are planar at 1.5K. Analysis of the SPD signals also indicates a planar anisotropy for all compositions at low temperatures. The temperature dependence of the anisotropy field [H.sub.A] is very similar for the Ga compounds whilst for the Sb compound a smoother dependence is observed at low temperatures. The anisotropy field increases irrespective of As or Sb substitution. The Curie point, saturation magnetization and anisotropy field can be simultaneously increased by changing the relative content of non-magnetic ions.

Detailed inelastic neutron scattering measurements of the phonon dispersion relations of a single crystal of bcc Fe, 10 at. % Be along the high symmetry directions [100], [110]. and [111] at room temperature are presented. The measurements demonstrate that the frequency of transverse phonons propagating along the [110] direction with a [110] polarization at the zone boundary is reduced by 10%with respect to bcc Fe.

Neutron powder diffraction between 315 and 8 K is used for examining the magnetic and crystal structures of the series FexMn(sub 5-x)Si3 (x=4,3.5,3,2,1). Fe3.5Mn1.5Si3 and Fe4MnSi3 have similar magnetic structures with low Curie point of below 240 K.

Magnetic structure of TbFe10V2 using magnetometry and high-resolution neutron powder diffraction is discussed. This shows that the behavior cannot be explained by a compensation effect and suggests that a canted, noncollinear magnetic structure develops below the spin-reorientation temperature.

Carries out a systematic study of the magnetic properties of the system Y[sub1-x]Pr[subx]Co[sub5] to clarify the role of 3d and 4f anisotropy in the occurrence of first-order magnetization processes and spin reorientation transitions in PrCo[sub5]. Information on spin reorientation transition temperatures; Presence of high-order terms in anisotropy energy expansion; Existence of competing anisotropies and consequent existence of effective anisotropy constants.

Studies the first-order field-induced magnetization transitions in single crystals. Details on the experiments; Results of the study; Conclusion.

Inelastic neutron scattering experiments are combined with infrared and Raman data to obtain a uniquely defined description of the intramolecular vibrations of three oligomers of polythiophene. Through refinement of ab initio force fields, the three vibrational spectra of each oligomer are simulated with remarkable accuracy. Two different basis sets of atomic orbitals are used: the first, is 6-31G* and is used to optimize the geometries and calculate the relevant force fields of α-2T and α-4T, the second is 3-21G* and is used for the same purpose for α-4T and α-6T. To improve agreement with the experiment, the force fields are scaled. In this way, one set of scaling parameters is generated for the 6-31G* basis and another for the 3-21G* basis. The parameters are common to both molecules calculated with either basis sets and are believed to be transferable to higher isomers. The fitting procedure is applied in steps: first, the calculated vibrational frequencies are assigned on the basis of the experimental infrared and Raman activity, then a fitting of the Inelastic Neutron Scattering profile is performed, finally, the infrared and Raman spectra are calculated with the new normal modes and the ab initio derivatives of the dipole moment and the polarizability. The procedure is iterated until the three spectra of each oligomer are satisfactorily reproduced. For α-4T, two scaled force fields are obtained—one for each basis set—and are shown to yield very similar normal modes. It is important to emphasize that not only the vibrational frequencies but also the spectral intensities are well reproduced by the simulations. Implicitly, this means that the dipole moment and the polarization tensor surfaces calculated ab initio at the potential energy surface minimum are of good quality. The procedure is absolutely general and can be applied to any molecular system. In the present case, it leads to well defined force fields that give... [ABSTRACT FROM AUTHOR]

Presents a study which investigated the crystal and magnetic structure of gallium substituted manganese aluminum alloys by neutron diffraction. Experimental method used; Measurement of the saturation magnetization and the anisotropy field; Influence of gallium substitution on the magnetic and structural properties.

Presents information on a study which examined the magnetic anisotropy and crystal structure of intermetallic compounds of the thorium manganese[sub12] structure using singular point detection technique and high resolution neutron powder diffraction. Advantage of the neutron diffraction technique; Structure determination; Variation of the iron sublattice anisotropy.

Reports on macroscopic magnetic measurements, Mössbauer spectroscopy and neutron diffraction investigation on single crystals of cobalt[subx] zinc[sub2-x]. Description of the crystalline structure; Contribution of cobalt ions to the anisotropy; Comparison between the measured integrated intensities and the intensities calculated on the basis of a Gorter's spin distribution.

Presents a systematic study of the effects of cobalt substitution on the crystal structure and magnetic anisotropy of Y[sub2]Fe[sub14-x]Co[subx]B and Nd[sub2] Fe[sub14-x] Co[subx]B to clarify the different roles and contributions to the anisotropy of both rare earth and transition metals. Preparation of the polycrystalline samples; Measurement of the effects of cobalt substitution on the tetragonal unit cell parameters.

Analyzes carbon monoxide, maganese and nickle substituted Fe3.34Ge2 hexagonal germanides to perform tructural (x-ray and neutron diffraction), Mossbauer, and magnetic investigations. Methodology used to conduct the study; Information on single crystal x-ray diffraction; Details on the neutron powder diffraction; Findings of the study.

We have used Time-of-Flight (ToF) neutron powder diffraction, and both [sup.57]Fe and [sup.119]Sn Mossbauer spectroscopy, to study the independent magnetic ordering behavior of the Fe and Ho sublattices in Ho[Fe.sub.6][Sn.sub.6]. The crystal structure of Ho[Fe.sub.6][Sn.sub.6] is orthorhombic (space group Immm). The Fe sublattice orders antiferromagnetically with a Neel temperature of 559(5) K, determined by differential scanning calorimetry. The ToF neutron diffraction patterns obtained at 30 K and 295 K show that the antiferromagnetic ordering of the Fe sublattice is along [100] with a propagation vector q = [010]. The magnetic space group of the Fe sublattice is Ipm'm'm' and the Fe magnetic moment at 30 K is 2.31(5) [[Mu].sub.B]. This magnetic structure is confirmed by our [sup.119]Sn Mossbauer spectra in which 37% of the Sn nuclei experience a substantial transferred hyperfine field from the Fe sublattice while the remaining 63% of the Sn sites show no magnetic splitting, due to the cancellation of transferred hyperfine fields from the Fe neighbors, in full agreement with our Wigner-Seitz cell calculations for each of the eight Sn sites in the Ho[Fe.sub.6][Sn.sub.6] structure. The Ho sublattice orders ferromagnetically at 9(1) K. ToF data obtained at 4 K show that the Ho moments are aligned along [001] i.e., perpendicular to the Fe ordering. The magnetic space group of the Ho sublattice is Im'm'm. The refined Ho magnetic moments at 4 K are 4.4(2) [[Mu].sub.B] and 5.2(2) [[Mu].sub.B] at the 2a and 4h sites, respectively. Index Terms--Magnetic structures, Mossbauer spectroscopy, neutron diffraction, rare-earth intermetallics.

Body centered cubic Fe1-xBex alloys are known to display an enhanced tetragonal magnetostriction compared to Fe. In order to characterize the enhanced magnetoelasticity observed in this alloy system, we present detailed inelastic neutron scattering measurements of the phonon dispersion relations of a single crystal of bcc Fe, 10 at. % Be along the high symmetry directions [100], [110], and [111] at room temperature. We observe in particular that the frequency of transverse phonons propagating along the [110] direction with a [110] polarization at the zone boundary is reduced by 10% with respect to bcc Fe (the corresponding elastic shear constant c′ = ½ (c11 - c12) associated with this mode is approximately 70% that of pure Fe). The dispersion of spin waves has also been determined for energy transfers up to 40 meV and is found to follow the isotropic dispersion relation E(q)=Dq², with D ~ 200 meV/Ų [for Fe, E(q)=Dq², with D=280 meV/Å2². [ABSTRACT FROM AUTHOR]

The effects of diluting Gd with Y on the magnetic properties of the giant magnetocaloric effect material Gd5Si2Ge2 have been investigated by high incident energy inelastic neutron scattering, magnetization, and x-ray powder diffraction measurements. The dynamic response for Gd5Si2Ge2 at 15 and 150 K consists of two magnetic excitations extending up to 40 meV. From the x-ray powder diffraction data, Gd4YSi1.9Ge2.1 is monoclinic at room temperature, space group P1121/a with the 4e site at x=-0.0092(3), y=0.1005(2), z=0.1808(4) almost exclusively occupied by Gd (97%), while the remaining four Gd/Y sites are randomly occupied by Gd and Y. The magnetization measurements show that the ordering temperature of Gd4YSi1.9Ge2.1 is about half that of Gd5Si2Ge2, as the former orders ferromagnetically at 149 K with an effective paramagnetic moment of 7.87μB. The observed magnetic dynamic response for the Gd4YSi1.9Ge2.1 at 7 K is also different from the nondiluted compound, whereby the positions and intensities of the magnetic excitations have decreased markedly with respect to Gd5Si2Ge2. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The magnetic and crystal structures of the series FexMn5-xSi3 (x=4,3.5,3,2,1) have been reinvestigated by neutron powder diffraction between 315 and 8 K. Fe atoms are found to preferentially occupy the 4d site of the hexagonal D88 structure (P63/mcm). The compound Fe4MnSi3 orders ferromagnetically below 300 K. Refinement of the neutron data for this compound indicates that the moments are aligned at ∼40° off the c axis. A high moment at the 6g site is due to a large Mn moment which is forced into a ferromagnetic alignment with the Fe moments. Associated with this moment is a moderate magnetic entropy change, with a maximum value of 4 J kg-1 K-1 for a magnetic field change of 5 T. The magnetic structure of Fe3.5Mn1.5Si3 is similar to that of Fe4MnSi3, but the Curie point is lower, below 240 K. A feature for this composition is the appearance of a spiral structure below 60 K. The compounds with x=1, 2, and 3 are all antiferromagnets with a spiral structure observed for Fe3Mn2Si3 at all temperatures up to the Néel point of 150 K. Two separate antiferromagnetic structures exist for Fe2Mn3Si3, one between 120 and 45 K and another structure for temperatures below 45 K. Similar features in the magnetic ordering are exhibited by FeMn4Si3. At temperatures between 70 and 95 K, the magnetic structure is similar to that of the low temperature phase of Fe2Mn3Si3. Accompanying the magnetic transition at 70 K is a structural distortion to space group Cmcm, a feature also observed for Mn5Si3. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The effects of diluting Gd with Y on the magnetic properties of the giant magnetocaloric effect material Gd5Si2Ge2 have been investigated by high incident energy inelastic neutron scattering, magnetization, and x-ray powder diffraction measurements. The dynamic response for Gd5Si2Ge2 at 15 and 150 K consists of two magnetic excitations extending up to 40 meV. From the x-ray powder diffraction data, Gd4YSi1.9Ge2.1 is monoclinic at room temperature, space group P1121/a with the 4e site at x=-0.0092(3), y=0.1005(2), z=0.1808(4) almost exclusively occupied by Gd (97%), while the remaining four Gd/Y sites are randomly occupied by Gd and Y. The magnetization measurements show that the ordering temperature of Gd4YSi1.9Ge2.1 is about half that of Gd5Si2Ge2, as the former orders ferromagnetically at 149 K with an effective paramagnetic moment of 7.87μB. The observed magnetic dynamic response for the Gd4YSi1.9Ge2.1 at 7 K is also different from the nondiluted compound, whereby the positions and intensities of the magnetic excitations have decreased markedly with respect to Gd5Si2Ge2. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Magnetic excitations in tetragonal HoCr[sub 2]Si[sub 2] have been measured by neutron spectroscopy. The temperature and Q dependence of the excitations measured at 8 K confirm that they can be attributed to crystal field (CF) dipolar transitions experienced by the Ho ion. The analysis of the neutron spectroscopy data for HoCr[sub 2]Si[sub 2] is simplified by the fact that the CF coefficients have already been determined for the series RX[sub 2]Si[sub 2] (R=rare earth, X=Cu, Ni) by neutron spectroscopy. In addition, electronic band structure calculations and experimental determinations of the electric field gradient for numerous compounds of the type RT[sub 2]Si[sub 2] (T=Cr, Cu, Ni) show that the first-order CF coefficient, A[sub 2][sup 0], changes sign when passing from the series RX[sub 2]Si[sub 2] (X=Cr, Ni) to RCu[sub 2]Si[sub 2]. In the light of this information, the available neutron spectroscopy data for HoCr[sub 2]Si[sub 2] are presented and discussed. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have used time-of-flight (TOF) neutron powder diffraction, and both [sup 57]Fe and [sup 119]Sn Mo¨ssbauer spectroscopy over the temperature range 2–600 K to determine the magnetic ordering mode of the Fe sublattice in YFe[sub 6]Sn[sub 6]. The crystal structure is orthorhombic (space group Immm). The Fe sublattice orders antiferromagnetically with a Ne´el temperature of 558(5) K. The TOF neutron diffraction patterns obtained at 4 and 293 K show that the antiferromagnetic ordering of the Fe sublattice is along [100] with a propagation vector q=[010]. The magnetic space group is I[sub P]m[sup ′]m[sup ′]m[sup ′]. This magnetic structure is confirmed by our [sup 119]Sn Mo¨ssbauer spectra. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]