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A surface acoustic wave (SAW) actuated rotary motor is reported here, consisting of a millimeter-sized spherical metal rotor placed on the surface of a lead zirconate titanate piezoelectric substrate upon which the SAW is made to propagate. At the design frequency of 3.2 MHz and with a fixed preload of 41.1 N, the maximum rotational speed and torque achieved were approximately 1900 rpm and 5.37 N-mm, respectively, producing a maximum output power of 1.19 W. The surface vibrations were visualized using laser Doppler vibrometry and indicate that the rotational motion arises due to retrograde elliptical motions of the piezoelectric surface elements. Rotation about orthogonal axes in the plane of the substrate has been obtained by using orthogonally placed interdigital electrodes on the substrate to generate SAW impinging on the rotor, offering a means to generate rotation about an arbitrary axis in the plane of the substrate. © 2011 American Institute of Physics.

A surface acoustic wave (SAW) actuated rotary motor is reported here, consisting of a millimeter-sized spherical metal rotor placed on the surface of a lead zirconate titanate piezoelectric substrate upon which the SAW is made to propagate. At the design frequency of 3.2 MHz and with a fixed preload of 41.1 N, the maximum rotational speed and torque achieved were approximately 1900 rpm and 5.37 N-mm, respectively, producing a maximum output power of 1.19 W. The surface vibrations were visualized using laser Doppler vibrometry and indicate that the rotational motion arises due to retrograde elliptical motions of the piezoelectric surface elements. Rotation about orthogonal axes in the plane of the substrate has been obtained by using orthogonally placed interdigital electrodes on the substrate to generate SAW impinging on the rotor, offering a means to generate rotation about an arbitrary axis in the plane of the substrate. © 2011 American Institute of Physics.

Structural and magnetic properties of the Li layered oxide, LiNi0.8Co0.1Mn0.1O2, have been studied by means of x-ray diffraction, dc magnetization, ac linear, and nonlinear susceptibility as well as by magnetic aging and temperature cycling experiments. A percolating spin system interacting via antiferromagnetic and ferromagnetic superexchange interactions of different strength induce a ferrimagnetic quasilong-range order with a transition temperature Tc ≈ 70 K, a Weiss temperature of −25 K and an effective magnetic moment of 2.07 μB. On cooling below Tc the two-dimensional (2D) triangular lattice built up of edge-sharing metal oxide octahedras first exhibits a 2D spin glass like behavior followed by complete spin frustration in three dimensions below 30 K. The findings correlate well with expectations for a ferrimagnetic reentrant cluster glass system as well as with predictions of the percolating cluster model.

In this paper we report results of structural, spectroscopic, and magnetic investigations of MgFe2O4 nanoparticles prepared by soft mechanochemical synthesis. MgFe2O4 nanoparticles crystallize in Fd3m space group with mixed cation distribution and reduced percentage of Fe3+ at tetrahedral (8a) sites. Discrepancy in the cation distribution compared to that in the bulk Mg-ferrite is one of the highest known. X-ray line broadening analysis reveals crystallite size and strain anisotropy. The saturation magnetization, M-sat=62 emu/g measured at 5 K is twice higher than that found in the bulk counterparts. Such high value of M-sat is attributed to the low value of cation inversion parameter (delta=0.69), to the core/shell structure of the nanoparticles and to the surface/volume ratio. Moumlssbauer spectrum collected at room temperature reveals ferrimagnetic ordering between Fe3+ ions in 8a and 16d sites, while zero-field-cooled (ZFC) and field-cooled (FC) M(T) measurements were shown superparamagnetic state above 350 K.

In this paper we report results of structural, spectroscopic, and magnetic investigations of MgFe2O4 nanoparticles prepared by soft mechanochemical synthesis. MgFe2O4 nanoparticles crystallize in Fd3m space group with mixed cation distribution and reduced percentage of Fe3+ at tetrahedral (8a) sites. Discrepancy in the cation distribution compared to that in the bulk Mg-ferrite is one of the highest known. X-ray line broadening analysis reveals crystallite size and strain anisotropy. The saturation magnetization, M-sat=62 emu/g measured at 5 K is twice higher than that found in the bulk counterparts. Such high value of M-sat is attributed to the low value of cation inversion parameter (delta=0.69), to the core/shell structure of the nanoparticles and to the surface/volume ratio. Moumlssbauer spectrum collected at room temperature reveals ferrimagnetic ordering between Fe3+ ions in 8a and 16d sites, while zero-field-cooled (ZFC) and field-cooled (FC) M(T) measurements were shown superparamagnetic state above 350 K.

In this paper we report results of structural, spectroscopic, and magnetic investigations of MgFe2O4 nanoparticles prepared by soft mechanochemical synthesis. MgFe2O4 nanoparticles crystallize in Fd3m space group with mixed cation distribution and reduced percentage of Fe3+ at tetrahedral (8a) sites. Discrepancy in the cation distribution compared to that in the bulk Mg-ferrite is one of the highest known. X-ray line broadening analysis reveals crystallite size and strain anisotropy. The saturation magnetization, M-sat=62 emu/g measured at 5 K is twice higher than that found in the bulk counterparts. Such high value of M-sat is attributed to the low value of cation inversion parameter (delta=0.69), to the core/shell structure of the nanoparticles and to the surface/volume ratio. Moumlssbauer spectrum collected at room temperature reveals ferrimagnetic ordering between Fe3+ ions in 8a and 16d sites, while zero-field-cooled (ZFC) and field-cooled (FC) M(T) measurements were shown superparamagnetic state above 350 K.

In this paper we report results of structural, spectroscopic, and magnetic investigations of MgFe2O4 nanoparticles prepared by soft mechanochemical synthesis. MgFe2O4 nanoparticles crystallize in Fd3m space group with mixed cation distribution and reduced percentage of Fe3+ at tetrahedral (8a) sites. Discrepancy in the cation distribution compared to that in the bulk Mg-ferrite is one of the highest known. X-ray line broadening analysis reveals crystallite size and strain anisotropy. The saturation magnetization, M-sat=62 emu/g measured at 5 K is twice higher than that found in the bulk counterparts. Such high value of M-sat is attributed to the low value of cation inversion parameter (delta=0.69), to the core/shell structure of the nanoparticles and to the surface/volume ratio. Moumlssbauer spectrum collected at room temperature reveals ferrimagnetic ordering between Fe3+ ions in 8a and 16d sites, while zero-field-cooled (ZFC) and field-cooled (FC) M(T) measurements were shown superparamagnetic state above 350 K.

In this paper we report results of structural, spectroscopic, and magnetic investigations of MgFe2O4 nanoparticles prepared by soft mechanochemical synthesis. MgFe2O4 nanoparticles crystallize in Fd3m space group with mixed cation distribution and reduced percentage of Fe3+ at tetrahedral (8a) sites. Discrepancy in the cation distribution compared to that in the bulk Mg-ferrite is one of the highest known. X-ray line broadening analysis reveals crystallite size and strain anisotropy. The saturation magnetization, M-sat=62 emu/g measured at 5 K is twice higher than that found in the bulk counterparts. Such high value of M-sat is attributed to the low value of cation inversion parameter (delta=0.69), to the core/shell structure of the nanoparticles and to the surface/volume ratio. Moumlssbauer spectrum collected at room temperature reveals ferrimagnetic ordering between Fe3+ ions in 8a and 16d sites, while zero-field-cooled (ZFC) and field-cooled (FC) M(T) measurements were shown superparamagnetic state above 350 K.

A systematic ab initio study of static ionic displacements in a face-centered-cubic Fe65Ni35 alloy has been carried out. Theoretical results for magnitudes of average Fe-Fe, Fe-Ni, and Ni-Ni < 110 > bond vectors agree well with experimental measurements. In addition, we have observed that in collinear ferrimagnetic states, iron-iron nearest-neighbor pairs with antiparallel local magnetic moments are shorter on average than those with parallel moments. Furthermore, having considered different states (ferromagnetic, nonmagnetic, and collinear ferrimagnetic states) for the same lattice spacing, we have shown that the magnetic structure strongly influences local geometrical properties of the alloy. For example, a transition from a ferromagnetic state to a collinear ferrimagnetic state induces a significant contraction of the volume associated with an iron site where the moment flips. A model system based on a Hamiltonian written as the sum of Lennard-Jones energies and a classical Heisenberg Hamiltonian has been introduced. It yields structural properties which are qualitatively similar to those obtained ab initio. We have found that some of the phenomena can be classified as magnetovolume effects.

In the search for new spintronic materials with high spin polarization at room temperature, we have synthesized an osmium-based double perovskite with a Curie temperature of 725 K. Our combined experimental results confirm the existence of a sizable induced magnetic moment at the Os site, supported by band-structure calculations, in agreement with a proposed kinetic-energy-driven mechanism of ferrimagnetism in these compounds. The intriguing property of Sr2 CrOs O6 is that it is at the end point of a metal-insulator transition due to 5d band filling and at the same time ferrimagnetism and high-spin polarization are preserved.

The compounds RNi2Mn (R=Tb, Dy, Ho, and Er) with a MgCu2-type structure have been synthesized. The R to transition metal atom ratio is confirmed to be 1:3 using the energy dispersive spectroscopy. The structural and magnetic properties have been investigated by various experimental methods. The x-ray diffraction patterns (XRD) can be well indexed with a cubic Laves cell and space group Fd3m. The refinement results of the XRD patterns show the presence of vacancies in the crystallographic structure. The ordering temperatures TC have been derived to be 131, 94, 75, and 50 K for R=Tb, Dy, Ho and Er, respectively, which are much higher than those of their corresponding RNi2 and RMn2 compounds. A large difference of M-T curves between zero-field-cooling and field-cooling magnetization for all samples at a certain temperature range is observed in a low field, which can be understood in the terms of narrow-domain-wall pinning and a sensitive temperature dependence of coercivity.

Cr 2p core excited x-ray absorption and x-ray magnetic circular dichroism (XMCD) spectra of ferromagnetic Cr1-δTe with several concentrations of δ=0.11-0.33 and ferrimagnetic Cr5S 6 have been measured. The observed XMCD line shapes are found to very weakly depend on δ for Cr1-δTe, The experimental results are analyzed by means of a configuration-interaction cluster model calculation with consideration of hybridization and electron correlation effects. The obtained values of the spin magnetic moment by the cluster model analyses are in agreement with the results of the band structure calculation. The calculated result shows that the doped holes created by the Cr deficiency exist mainly in the Te 5p orbital of Cr1-δTe, whereas the holes are likely to be in the Cr 3d state for Cr5S6.

The patent describes a method and means for phase trimming of ferrimagnetic, latching phase-shifters in a waveguide without any electronic drive adjustments by running the drive-wire of the ferrimagnetic core through a second ferrimagnetic material external to the waveguide.

The molecular field coefficients employed in the Neel theory of ferrimagnetism have been determined as functions of the levels of diamagnetic ion substitution in the garnet family (Y(z)Gd(3-z))(R(x)Fe(2-x))(Q(y)Fe(3-y)) O(12), where R and Q represent diamagnetic octahedral and tetrahedral substitutions, respectively. With these coefficients the magnetic moment versus temperature curves of compositions ranging from 0 = or x = or 0.70, 0 = or y = or 1.95, and 0.40 = or z = or 1.00 were computed and are presented in this report.

A new ferrimagnetic single-crystal sphere orientation device has been developed for use with a variety of sphere sizes and compositions. Similar to other instruments which operate on a magnetic principle, this orienter provides (110) axes alignments. However, with one small electromagnet, it is considerably simpler than previously reported instruments of this type. From theoretical considerations, it is concluded that high alignment sensitivity will be obtained for polished spheres of low mass density, small radius, high magnetocrystalline anisotropy, and low coefficient of friction between sphere and support. It is also concluded that the sphere should be supported in cavities of conical geometry, with the cone angle as small as possible. The results of both x-ray analysis and microscope visual observation with a number of typical spheres indicate that the combination of accuracy and reliability of the instrument is superior to that of the other devices and suggests that the factors controlling the alignment sensitivity as derived from theory are at least qualitatively correct.

In the past few years, considerable research has been conducted on binary and ternary alloy systems of the 3d transition elements with metals of the rare-earth group (elements with nuclear charge 21, 39 and 57 through 71). These studies have revealed many new ferro- and ferrimagnetic substances. The most impressive of these new alloys are those based on the hexagonal intermetallic cobalt rare-earth (RE) compounds Co5RE. In this paper, the authors present new designs which use these materials in the development of a compact electronically tunable high field dc magnet for use in microwave filters and power limiters as well as in the design of power generators for use in artillery fuzing applications.

The normal spinel Fe(Cr2)S4 has been studied using the Mossbauer effect. Spectra have been collected over the temperature range 2-500K. Results are presented for the quantity (e squared)qQ/2, the hyperfine field, and the isomer shift. Experiments in applied fields at 7 and 81K show that the quadrupole interaction is not produced by a crystallographic distortion. Attention is drawn to features of the spectra which suggest the presence of relaxation effects in the compound. The isomer shift shows deviations from the Debye model behavior. A model, which allows explanations of the observations, is proposed. (Author), Revision of report dated 29 Oct 71.

A three sublattice ferrimagnetic model for Ga(2-x)F(x)O3 is shown to explain all the presently available magnetic data. The x dependence of the iron occupation of the various sublattices is obtained, and the x dependence of the magnetization and the Curie temperature is calculated. All of these agree quite well with experimental data. It is shown that the magnetoelectric effect does not contribute (in the order considered) to the various material constants. Most of the elastic, piezoelectric, and dielectric constants of GaFeO3 are measured.

The electronic structure of uranium ions in insulating host materials has been determined, enabling one to explain the magnetic behavior of the uranium iodide and oxide compounds. The optical properties of the laser ion, chromium, in GdAlO3 have been explained. The cause of the anomolous behavior of the magnetic susceptibility of Ce compounds has been understood. The behavior of helimagnets in magnetic fields has been studied and the phase diagrams in external magnetic fields have been constructed. The electronic conductivity of a one-dimensional model for a substitutional alloy and of a multilayer semiconductor has been determined. Finally, new methods for the solution of the transport equation in solids have been developed and applied in the areas of heat transport through insulators and neutron transport through reactors. (Author)

A laminar subsidiary resonance limiter that reduces the threshold power level for limiting by an order of magnitude was developed. The design was derived from a computer investigation of the effects of ferrite demagnetizing factors on threshold power level for ferromagnetic limiting. Minimum threshold power level is achieved when the demagnetizing factor in the direction of the applied dc biasing field is zero. This occurs only in a needle geometry. Multiple needles are required to provide sufficient ferromagnetic material for effective limiting. A laminar design consisting of alternate ferromagnetic and dielectric rods is used to obtain dc magnetic field isolation between the ferrite rods. This design gives the desired magnetic field demagnetizing factors while providing a dominant mode propagation path for the microwave signal. An X-band limiter was developed. It consists of 11 rectangular YIG rods separated by dielectric rods of the same dimensions and mounted on the narrow side of RG-52/U X-band waveguide. A combination of polycrystalline YIG and single-crystal YIG rods is used to increase the dynamic range of the limiter. The waveguide structure also effectively eliminates high-loss magnetostatic modes. The limiter has threshold power of 2.8 watts and a dynamic range of 30 dB. The insertion loss is less than 0.5 dB over the frequency range of 8.5 to 9.4 GHz. (Author)

A ferrite-varactor limiter combination operating at X band was investigated. The ferrite limiter portion of this package employs a combination of polycrystalline YIG, for dynamic range, and single-crystal YIG, for reduced threshold. Various design techniques employing ridge waveguide and dielectric loaded ferrite limiters were studied. The ferrite-varactor package has a threshold of about 30 mW and a dynamic range up to 10 kW. The overall insertion loss is less than 1.0 dB in the frequency range of 8.9 to 9.5 GHz. The flat leakage is about 30 mW and the spike leakage energy is less than 0.3 erg at 10 kW of peak power input. (Author)

The following two vapor deposition metalizing techniques were developed for metalizing ferrimagnetic materials: (1) Evaporating approximately 6000 Angstrom units of iron, (2) Sputtering approximately 5000 Angstrom units of nickel. It was advantageous to electrodeposit about 0.0001 inch nickel on the vapor deposited films. Nickel ferrite and yttrium iron garnet toroids were fabricated and brazed to Kovar, copper and titanium mating members using a vacuum brazing furnace equipped with an induction coil. The parts to be brazed were placed inside a box-like nickel container which, in turn, was placed in the induction coil. Incusil 15 and copper-silver eutectic braze alloys were used. Relatively strain-free brazes were made between ferrimagnetic materials and both copper and titanium. Strain could not be eliminated when brazing to Kovar. No significant changes in either saturation magnetism or linewidth as a result of the brazing operation were observed. An increase in dielectric loss tangent was observed when nickel ferrite was metalized with evaporated iron. No changes in dielectric loss tangent were observed when sputtered nickel films were used as metalizing. (Author)

The research carried out under this grant is summarized. The two principal studies have been (1) the development of a general random-phase theory for anisotropic spin systems, and (2) the investigation of a systematic series of truncation schemes for Green's function theories. (Author)

A summary of the phases is presented which occur in the systems Gd, Sm, Dy, Ho, Er-Mn. In all these systems the phases REMn2, REMn4 (RE6Mn23 or REMn5) and REMn12 exist (the compound SmMn12 has, up to now, not been detected). The phases HoMn2 and ErMn2 possess (at least at room temperature) the same structure (MgCu2) as the other REMn2 compounds. The lattice spacings of the compounds diminish continously with atomic number. By DTA the systems Gd-Mn and Dy-Mn have been studied and phase diagrams constructed. The X-ray investigations and X-ray fluorescence analysis agree with these diagrams. Magnetic measurements with Y, Sm, Dy, Ho and Er-Mnx (x = 3, 83 - 5) yielded accurate Curie-points. The saturation magnetization of YMn5 and SmMn5 is higher than the values of literature. By measurements of the paramagnetic properties of SmMn5 and HoMn5 above the Curie temperature the fact that these compounds are ferrimagnetic and not ferromagnetic could be established. The results are discussed in terms of the theory of ferrimagnetic substances., Available copy will not permit fully legible reproduction. Reproduction will be made if requested by users of DDC. Copy is available for public sale.

A study of magnetoelastic surface wave phenomena in ferrimagnetic crystals is being carried out to assess their use in signal processing systems. During this first year 100 MHz and 200 MHz fundamental-frequency surface wave delay lines on LiNbO3 and quartz have been constructed, and a small magnetoelastic attenuation observed when a YIG slice is bonded to the LiNbO3 and an appropriate magnetic field applied. A partial theoretical analysis of the interaction has been made and various effects predicted for different geometries. (Author)

The present work describes two novel magnetic composite catalysts, synthesized by functionalizing the silica/iron oxide composite surface with sulfaguanidine and sulfadiazine. The sulfaguanidine functionalized catalyst was found to be very efficient for multicomponent coupling reactions of phenylacetylene with various aldehydes and amines. The sulfadiazine functionalized catalyst was successfully applied in the synthesis of various 1,8-dioxo-octahydroxanthenes in water. Both the sulfaguanidine and sulfadiazine functionalized catalysts were very active and selective in the alkylation of toluene with benzyl chloride. © 2018 American Chemical Society.