Search

The microstructural effects on the mechanical and electrical properties of common density PZT95/5-2Nb materials under shock compression were investigated. The results indicate that differences in the porous microstructure of common density materials have little effect on mechanical and electrical shock properties.

The Nd2Fe14B single-layer and [(NdFeB)(sub x)/ (Nb, Cr)](sub n) multilayer magnetic properties and microstructure are compared in order to discuss the film magnetization reversal using the modified nucleation and pinning models. The Nb Spacer layer enriched the grain boundaries of the Nd3Fe14B phase, which in turn inhibited the grain growth.

The effect of structural and domain pattern changes upon annealing on the magnetoimpedance (MI) effect of Fe73.5Cu1Nb3Si13.5B9 amorphous ribbons is reported. The maximum MI effects are related to the optimum combination of soft properties with the transverse domain patterns.

Vortex pinning is studied for the superconducting Nb film covering ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy. Large enhancement in pinning the Nb film is observed in the final dendrite-shaped magnetic domains.

The linear increase of the current perpendicular to plane (CPP) resistance with the number of bilayers in both normal and superconducting Nb/Co multilayers is presented. The unit area resistance of one pair of Co/Nb interfaces were found to be 3.5 plusmn 0.7 and 6.3 plusmn 0.9 f omega m(super 2) for normal and superconducting Nb, respectively.

The magnetoresistance (MR) and thermal behaviors of the new magnetic tunnel junctions (MTJ) structures comprising CoNbZr layers are investigated. Thin CoNbZr films were used as an underlayer in order to get ultrasmooth interfaces for the bottom electrode, which was beneficial for reducing temperature-dependent TMR properties and by adjusting the bottom electrode thickness, TMR ratio of 32% was achieved.

Repulsive Meissner interaction between the magnetic tip and sample is used for determining the critical temperature of a superconducting Nb film. Vortex creation by the stray field of the tip with two vortices that are nucleated simultaneously and in succession is observed.

The magnetoresistance (MR) and thermal stability of new spin valve (SV) structure consisting of CoNbZr layers upon exposure to post-deposition annealing at elevated temperatures are examined. The MR ratio increased by nearly 50 percent from 4.5 percent to 6.8 percent and the exchange bias field increased by 52 percent from 294 Oe to 448 Oe for CoNbZr-based SV after annealing at 300 degree C for 240 min.

The phase stability and soft magnetic properties of amorphous CoNbZr films with Pd are examined. Excellent magnetic characteristics with a coercive force of 0.54 Oe and an anisotropy field of 11 Oe are observed in the film with the addition of 4.34 percent Pd.

The investigation of the microstructure and magnetic properties of Pr2Fe14B/alpha-Fe nanocomposites with small amount of Tb, Nb and Zr additions is discussed. Optimum magnetic properties with room temperature coercivity of 8.2 kOe and maximum energy product of 20.3 MGOe are observed in Pr7Tb1Fe87Nb0.5Zr0.5B4 ribbons.

A series of Co/Nb bilayers, Nb/Co/Nb and Co/Nb/Co trilayer thin films are made by dc sputtering. Magnetic hysteresis loops are measured to study the interplay between superconductor and ferromagnet, and the result shows the influence of large exchange field and small spin-orbit interaction on superconductivity.

Magnetic properties of R(Fe(sub 1-x)Co(sub x))(sub 11.3)Nb(sub 0.7) compounds are investigated. The unit cell volume slightly decreases with increasing Co content for both systems.

Pb[([Zr.sub.0.52][Ti.sub.0.48]).sub.0.96][Nb.sub.0.04][O.sub.3] (PZTN) thin films are deposited on BaPb[O.sub.3] (BPO) electrodes of different thicknesses by rf-magnetron sputtering. The studies have shown that the tensile stress in the films have originated from the phase transformation stresses and the ferroelectric and dielectrics properties are improved with the raise of tensile stresses.

Overdamped NbTiN Josephson junctions with Ti-TiN bilayered normal-metal barrier are described for metrological applications. Optimization of the NbTiN film is described in terms of stress for preparing circuits containing large number of junctions.

Several studies are conducted to explain the flux-closure pattern that is demonstrated by a two-dimensional NbN-Fe superconductor-ferromagnet nanocomposite. The anisotropy exhibited by the angular magnetoresistance of the compound is shown to get highly suppressed at high fields.

The strain mediated microwave magnetoelectric coupling taking place in the bilayers of peizoelectrics and ferrites with cubic magnetocrystalline anisotropy is analyzed. The bilayers of nickel zinc ferrite and lead zinc niobate-lead titanate are shown to exhibit the highest magnetoelectric coefficient.

Nb thin films containing a regular square array of antidotes spacing are prepared by using a relatively simple lithographic process. The behavior of the critical current density as well as the position of the maxima is shown to be consistent with the ones calculated in the framework of the time dependent Ginzburg-Landau model.

The article explains the synthesis and the structural, dielectric and magnetic properties of the multiferroic [Ba.sub.4][Bi.sub.2][Fe.sub.2][Nb.sub.8][O.sub.30] compounds. The coupling behaviour exhibited by the compounds is also analyzed.

The measurements of the magnetic susceptibility, electrical resistivity and heat capacity are described for the polycrystalline YbNi[Al.sub.4] intermetallic compound. X(T) is measured up to 1000 K and its behavior is shown to be typical of a compound with the valence fluctuation between [Yb.sup.3+ ] and [Yb.sup.2+].

PbO-MgO-[Nb.sub.2][O.sub.5]-Ti[O.sub.2] (PMNT) pyrochlore thin films are prepared on Pt-coated silicon substrates by using radio-frequency magnetron sputtering and postdeposition annealing method. The pyrochlore-structured PMNT thin films have displayed ultralow dielectric losses, with very low loss tangent and relatively high dielectric constants, and the relative permittivity has increased upon cooling without any signature of a structural phase transition.

Several contact and noncontact methods are employed to explain the different giant magnetoimpendance effects observed in the nanocrystalline ribbons. The effects of different frequencies and magnetic fields on the discussed magnetoimpedance are also analyzed.

Several studies are conducted to explain the impact of the changes taking place in the B and Si contents on the glass-forming ability and soft-magnetic properties in [(Co.sub.0.89][Fe.sub.0.057][Nb.sub.0.053]).sub.100?x][([B.sub.0.8][Si.sub.0.2]).sub.x] glassy alloys. An increase in the B and Si contents is shown to lead to a significant enhancement in the thermal stability of the supercooled liquid.

The properties and applications of the various FeCoBSiNb bulk glass alloys prepared using commercial raw materials via the optimization of the Nb content are explained. These alloys are shown to exhibit extremely high saturation magnetization and low coercive force.

The article explains the synthesis and the properties of the various self-doped [La.sub.1- x]Mn[O.sub.3]/y- wt- %Nb- SrTi[O.sub.3] heteroepitaxial junctions. The magnetically tunable properties of the films are shown to be completely related to the annealing time.

Several studies are conducted to explain the various effects of the ultrathin transition metal buffer layers on the growth of the [Fe.sub.3][O.sub.4] thin films. The buffers are shown to lead to anomalous magnetic properties in these films.

The significance of the different misorientation and coincident site lattice boundaries in the functioning of the Goss-textured Galfenol rolled sheet is demonstrated. The magnetostrictive variation observed in the compounds is also analyzed.

The article explains the synthesis and the properties of the various self-doped [La.sub.1- x]Mn[O.sub.3]/y- wt-% Nb- SrTi[O.sub.3] heteroepitaxial junctions. The magnetically tunable properties of the films are shown to be completely related to the annealing time.

The dynamic properties of the [([Co.sub.0.85][Nb.sub.0.15]).sub.100-x][Nd.sub.x] soft magnetic thin films are examined in a wide frequency range. Strong enhancement of the damping parameter, a key materials parameter controlling the dynamic response and the full width at half maximum of imaginary permeability spectra, is observed when Nd element is doped.

Ferromagnetic resonance spectroscopy is used to study the dependence of the magnetic anisotropy on the electric field (E-field) for [Fe.sub.3][O.sub.4]/PZN-PT (lead zinc niobate-lead titanate) multiferroic heterostructures obtained through a sputter deposition process. The large E-field tunable magnetic properties exhibited by the [Fe.sub.3][O.sub.4]/PZN-PT multiferroic heterostructures provide significant potential for novel electrostatically tunable multiferroic devices.

A study was conducted to examine the structural and magnetic properties of Fe-Nb-B amorphous/nanocrystalline alloys obtained by compaction of mechanically alloyed powders. Scanning electron microscopy images revealed that the presence of amorphous phase enhanced the quality of compaction.

The article explains the structure and formation of a dimensionally gradient magnetoelectric (ME) bimorph sensor that is shown to exhibit a wide frequency and magnetic dc bias operating range. A change in the tip mass of the composite is shown to lead to a significant shift in the operating frequency range of the sensor.

The studies related to the magnetism-induced ferroelectricity in the E-type orthorhombic HoMn[O.sub.3] (o-HMO) films grown on Nb-doped and undoped SrTi[O.sub.3](001) substrates is presented. The temperature dependent magnetization in the films is observed to exhibit an antiferromagnetic ordering around 44 K and an anomalous second magnetic ordering along the c-axis near 35 K.

Microstructure and polarization degradation are seen under cyclic electric loadings for [001]-oriented Pb([Mg.sub.1/3][Nb.sub.2/3])[O.sub.3]-PbTi[O.sub.3] single crystals. Microcracking and phase transition has hindered ferroelectric domain switching and has reduced the number of electric dipoles that has switched under cyclic electric field.

Dielectric characteristics of [Ba.sub.6]Co[Nb.sub.9][O.sub.30] tetragonal tungsten bronze ceramics are analyzed. The nonlinear magnetic hysteresis curve is seen in [Ba.sub.6]Co[Nb.sub.9][O.sub.30] ceramics at 5 K, which has shown the soft magnetic behavior that is related to the tetragonal tungsten bronze crystal structure containing magnetic ions of [Co.sup.3+].

The temperature dependence of magnetic properties of nanocrystalline [Fe.sub.60][Co.sub.18][Cu.sub.1][B.sub.15][Nb.sub.6-x][Zr.sub.x] (x=0, 3, 6) alloys is studied at different stages of devitrification. Thermal dependence of the exchange stiffness constant is obtained from the measurement of specific magnetization and coercivity as a function of crystalline fraction and temperature for the three studied alloys.

A highly sensitive method is developed for obtaining the permeability of magnetic film without a limitation of sample size, which is based on the electrical impedance of magnetic film in contact with a copper conductor. The permeability of the CoNbZr thin film is evaluated and the measured values have corresponded to those obtained by the Landau-Lifshitz-Gilbert equation.

The interface resistance in Ni/Nb multilayers prepared by sputtering system is analyzed. The current perpendicular to plane (CPP) measurement interpreted with a one-band series-resistor model is used for obtaining the CPP resistivities of Nb and Ni and the unit area resistances for superconducting and normal Ni/Nb interfaces.

Polycrystalline samples of [Ru.sub.1-x][Nb.sub.x][Sr.sub.2][Eu.sub.1.4][Ce.sub.0.6][Cu.sub.2][O.sub.10-[delta]] are prepared by conventional solid state reaction by using stoichiometric amounts of high purity Ru[O.sub.2], [Nb.sub.2][O.sub.5], SrC[O.sub.3], [Eu.sub.2][O.sub.3], Ce[O.sub.2] and CuO powders. The critical temperatures, including the onset, intergrain and intragrain transition and [T.sub.R=0] transition temperatures, have depended on the Nb content, microstructure and applied magnetic field.

The simplified vibrating sample magnetometer is fabricated and the trapped magnetic flux in Nb superconducting thin film is measured by vibrating sample near the search coil. Many vortices are trapped in the perimeter of the sample when a perpendicular magnetic field is applied and the studies have confirmed that Josephson current is modulated by the parallel magnetic field generated by the vortices.

The intercomparison of the superconductivity of Mg[B.sub.2], Al[B.sub.2], Nb[B.sub.2+x] is presented. The nonstoichiometry has induced an increase in c parameter with Boron excess both in Nb[B.sub.2+x] and Ta[B.sub.2+x] and magnetization and resistivity measurements in case of niobium boride samples have shown the absence of superconductivity in stoichiometric Nb[B.sub.2] sample.

(1-x)([Bi.sub.0.9][La.sub.0.1])Fe[O.sub.3]-xPb([Fe.sub.0.5][Nb.sub.0.5])[O.sub.3] (BLFO-PFNO) are examined as an A-site substituted counterpart multiferroic solid solution. The BLFO-PFNO solid solution system has enabled soft ferromagnetism at room temperature and macroscopic polarization with the ferroelectric domain evolution due to nanoscale ordered single grains at high composition of relaxor-type ferroelectric PFNO.

The traditional solid state reaction method is used for preparing perovskite solid solution ceramics and ferroelectric and dielectric measurements have shown that these samples are relaxor type ferroelectric materials. The ac susceptibility measurement has showed that the peak position is dependent on frequency, thus indicating a glassy or relaxor type behavior and describing the 0.9Pb([Fe.sub.0.5][Nb.sub.0.5])[O.sub.3]-0.1PbTi[O.sub.3] to be a magnetoelectric relaxor material.

The current-voltage characteristics and magnetotransport properties of [La.sub.0.7][Sr.sub.0.3]Mn[O.sub.3]/Nb(1.0%):SrTi[O.sub.3] junctions under various currents and different temperatures ranges are examined. The resistance, magnetoresistance and electroresistance of the junctions are dependent on bias-current direction, current, magnetic field and temperature.

Magnetic properties and microstructure of directly quenched [Nd.sub.9.5][Fe.sub.72.5][Ti.sub.3-x][M.sub.x][B.sub.15] (M=Nb and Zr) bulk magnets in rod form with a diameter of 0.9 mm are analyzed. Proper Nb or Zr substitution for Ti has modified phase constitution and has refined the grain size effectively and their high permanent magnetic property has occurred from the existence of a large volume fraction of 2:14:1 phase, finer grain size and the existence of grain boundary phase.

The phase evolution, microstructure, and magnetic properties of melt spun Sm[Co.sub.7-x][Nb.sub.x] (x = 0-0.6) ribbons are examined by using powder, x-ray diffraction, transmission electron microscopy and vibrating sample magnetometer. The mechanism of the coercivity enhancement is discussed along with its optical magnetic properties.

A strong magnetoelectric (ME) interaction is described in a magnetostrictive-semiconductor-piezoelectric heterostructure consisting of the Huesler alloy, [Co.sub.2]MnAl, GaAs, and lead magnesium niobate-lead titanate (PMN-PT). A large ME coupling is obtained and static magnetization measurement has shown a reduction in the remanence magnetization while applying the electric field, which has corroborated the ME interactions mediated by the translation of magnetoelastic forces in this structure.

The temperature stability of field induced uniaxial anisotropy ([K.sub.U]) is examined by thermomagnetic treatments of [([Co.sub.1-x][Fe.sub.x]).sub.89][Zr.sub.7][B.sub.4] amorphous ribbons after field annealing below and the above the crystallization temperature. Field crystallization is required for elevated temperature applications when field induced anisotropy is vital for performance.

The field-induced magnetic anisotropy ([K.sub.u]) and the hyperfine interactions in nanocrystalline [Fe.sub.94-x][Nb.sub.6][B.sub.x] alloys are examined with respect to the origin of [K.sub.u] in the bcc-Fe/amorphous soft magnetic nanostructures. The relatively large [K.sub.u] value estimated for the bcc nanocrystallites is attributed to a possible local tetragonal distortion induced by the interstitial B atoms.

The power supply efficiency can be improved by using the glassy metal alloy [Fe.sub.77][P.sub.7][B.sub.13][Nb.sub.3] powder in an inductor core. The heat generation in the core is suppressed by using the low loss power and it has become easy to design a temperature rise in the entire power supply circuit.

The effect of [B.sub.2][O.sub.3] flux melting on the soft magnetic properties of [([Fe.sub.0.75][B.sub.0.20][Si.sub.0.05]).sub.96][Nb.sub.4] bulk metallic glass prepared by casting is examined. The results have shown that it is possible to develop a new soft magnetic material that has displayed constant permeability with low core loss.