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The possibility of inducing the collinear antiferromagnetism by introducing nonmagnetic ions into the lattice of SrFe[O.sub.(3-delta)] is explored. The study shows that the addition of a non-magnetic cation such as [Ti.sup.4+] helps in reducing the complexity of the magnetic structure with a single magnetic ion, enabling a simpler understanding of the physics behind such transformations.

A systematic study of the effect of depositing CoFe2O4 (CFO) films of various thicknesses (d = 0-600 nm) on the giant magneto-impedance (GMI) response of a soft ferromagnetic amorphous ribbon Co65Fe4Ni2Si15B14 has been performed. The CFO films were grown on the amorphous ribbons by the pulsed laser deposition technique. X-ray diffraction and transmission electron microscopy revealed a structural variation of the CFO film from amorphous to polycrystalline as the thickness of the CFO film exceeded a critical value of 300 nm. Atomic force microscopy evidenced the increase in surface roughness of the CFO film as the thickness of the CFO film was increased. These changes in the crystallinity and morphology of the CFO film were found to have a distinct impact on the GMI response of the ribbon. Relative to the bare ribbon, coating of amorphous CFO films significantly enhanced the GMI response of the ribbon, while polycrystalline CFO films decreased it considerably. The maximum GMI response was achieved near the onset of the structural transition of the CFO film. These findings are of practical importance in developing high-sensitivity magnetic sensors. [ABSTRACT FROM AUTHOR]

Research into the synthesis and characterization of polycrystalline RuSr2GdCu2O8 materials is presented. It is concluded that flux lattice dynamics dominate the response in the superconducting state.

The present work has been carried out to study the suitability of milk dairy waste scum (MDWS) biodiesel as a fuel for diesel engine. The investigations were carried out on performance, emission and combustion characteristics of a direct injection dual cylinder diesel engine fueled with MDWS methyl ester, and their blends. Two-step transesterification process was used to synthesize the MDWS biodiesel, characterization according to specified ASTM D6751-15C standards. The performance characteristics studies showed an increased brake thermal efficiency of B20 (3%) and B30 (0.94%) blends in comparison to fossil diesel. However, the increased brake specific fuel consumption (BSFC) was also found with all the fuel blends and an higher (9%) BSFC was obtained with B50 compared to diesel fuel at full load condition. The emissions of blends were found to be lower in comparison with diesel fuel, except for nitrogen oxides. A 32% increase in NOx emission was found with B50 blend compared to diesel fuel at maximum load condition. However, improved combustion characteristics would found with MDWS blends with respect to in-cylinder pressure, ignition delay, and heat release rate compared to fossil diesel. [ABSTRACT FROM AUTHOR]

A novel resonant method based on a tunnel-diode oscillator is used to study the dynamic transverse susceptibility in a Fe nanoparticle system. Characteristic peaks at anisotropy fields are observed and their temperature evolution shows a systematic trend.

SrFe12O19/La1-xCaxMnO3 (SFO/LCMO) composites with x = 0.1 and 0.5 were synthesized via a two stage combined citrate precursor sol-gel and hydrothermal method. The structure and composition of the samples were refined from the X-ray diffraction patterns. The morphologies of the composites were investigated using transmission and scanning electron microscopies, which revealed micron-sized hexagonal platelets of SFO with LCMO particles with average diameters of 110-130 nm formed at the surface. An investigation of the temperature and field dependence of the magnetization found that the SFO phase with a ferrimagnetic characteristic up to 720 K dominates the magnetic properties of the composite samples. The SFO/LCMO composite samples showed a reduction in saturation magnetization and coercivity when compared with pure SFO. However, low temperature hysteresis loops recorded after cooling in applied fields up to 5 T revealed the absence of exchange bias in the SFO/LCMO composite, ruling out the possibility of significant interfacial magnetic coupling between SFO and LCMO. [ABSTRACT FROM AUTHOR]

Improving the sensitivity of existing biosensors for highly sensitive detection of magnetic nanoparticles as biomarkers in biological systems is an important and challenging task. Here, we propose a method of combining the magneto-resistance (MR), magneto-reactance (MX), and magneto-impedance (MI) effects to develop an integrated magnetic biosensor with tunable and enhanced sensitivity. A systematic study of the 7 nm Fe3O4 nanoparticle concentration dependence of MR, MX, and MI ratios of a soft ferromagnetic amorphous ribbon shows that these ratios first increase sharply with increase in particle concentration (0-124 nM) and then remain almost unchanged for higher concentrations (124 nM-1240 nM). The MX-based biosensor shows the highest sensitivity. With this biosensor, ∼2.1 × 1011 7 nm Fe3O4 nanoparticles can be detected over a detection area of 2.0 × 105 μm2, which is comparable to a superconducting quantum interference device biosensor that detects the presence of ∼1 × 108 11 nm Fe3O4 nanoparticles over a detection area of 6.8 × 104 μm2. The proposed biosensor can detect low and various concentrations of superparamagnetic nanoparticles (below 10 nm in size), which is of practical importance in biosensing applications. [ABSTRACT FROM AUTHOR]

We report the observation of contrasting magnetic behavior in cobalt ferrite (CFO) thin films deposited on single crystalline magnesium oxide (MgO) and strontium titanate (STO). Epitaxial films on MgO (100) with a lattice mismatch of 0.35% showed out-of-plane anisotropy whereas the films on STO (100) with a lattice mismatch of 7.4% displayed in-plane anisotropy. Stress anisotropy calculated from angle-dependent x-ray diffraction analysis confirmed that the change in anisotropy originates from the lattice mismatch. An additional low-field switching characteristic is observed in the M-H loops of the CFO films, which became prominent with lowering temperature as also evidenced from the rf transverse susceptibility measurements. The obtained results revealed that the low field switching is associated with the film-substrate interface. [ABSTRACT FROM AUTHOR]

The influence of first- and second-order magnetic phase transitions on the magnetocaloric effect (MCE) and refrigerant capacity (RC) of charge-ordered Pr0.5Sr0.5MnO3 has been investigated. The system undergoes a paramagnetic to ferromagnetic transition at TC∼255 K followed by a ferromagnetic charge-disordered to antiferromagnetic charge-ordered transition at TCO∼165 K. While the first-order magnetic transition (FOMT) at TCO induces a larger MCE (6.8 J/kg K) limited to a narrower temperature range resulting in a smaller RC (168 J/kg), the second-order magnetic transition at TC induces a smaller MCE (3.2 J/kg K) but spreads over a broader temperature range resulting in a larger RC (215 J/kg). In addition, large magnetic and thermal hysteretic losses associated with the FOMT below TCO are detrimental to an efficient magnetic RC, whereas these effects are negligible below TC because of the second-order nature of this transition. These results are of practical importance in assessing the usefulness of charge-ordered manganite materials for active magnetic refrigeration, and Pr0.5Sr0.5MnO3 provides an interesting case study in which the influence of first- and second-order transitions on MCE could be compared in the same system in a single experiment. [ABSTRACT FROM AUTHOR]

Electrical conductivity, magnetic susceptibility, and point contact Andreev reflection (PCAR) studies were done on bulk, polycrystalline SrRu1-x(TM)xO3 (TM=Cr, Mn, Ti) and SrRu0.92O3 with a high degree of disorder. Fits of the temperature dependence of the latter using the Curie–Weiss law yielded values for the Curie–Weiss temperature, Θ. Furthermore, the values of the Curie temperature, TC were identified by determining the maximum susceptibility as a function of temperature. PCAR measurements were done to determine the transport spin polarization, Pt (0≤Pt≤1.0). Pure SrRuO3 undergoes ferromagnetic ordering at a Curie temperature of TC∼160 K and has a relatively high spin polarization (∼0.6). Our results indicate that when the lattice is disordered from either the presence of Ru lattice site defects or the substitution of a transition metal for the Ru, TC changes by a factor of 2, and Θ by a factor of 1.7. By contrast, the spin polarization is unchanged for both SrRu0.94Ti0.06O3 and SrRu0.9Mn0.1O3, while it is barely changed (P=0.5) for SrRu0.9Cr0.1O3. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles embedded in polymer matrices have excellent potential for electromagnetic device applications like electromagnetic interference suppression. We have synthesized polymer nanocomposites of poly(methylmethacrylate) doped with varying concentrations of iron nanoparticles (∼20 nm in size). The iron nanoparticles were produced using a microwave plasma technique and have a natural oxide surface layer for passivation. These nanocomposites were processed using melt blending technique. The polymer processing conditions were optimized to achieve good uniform dispersion of the nanoparticles in the polymer matrix. The concentration and dispersion of nanoparticles were varied in a controlled way. Surface characterization with scanning electron microscopy indicates that, to a large extent, the iron nanoparticles are embedded in the bulk; the surface mainly showed features associated with the polymer surface. Static magnetic properties such as susceptibility and M–H loops were studied using a physical property measurement system. The variation of the ferromagnetic response was consistent with the varying volume concentration of the nanoparticles, the polymer itself contributing a diamagnetic response. At room temperature, hysteresis loops exhibited a somewhat large coercivity (260 Oe) associated with a surface oxide layer on the particles. Overall, the excellent dispersion coupled with reasonable control over magnetic properties achieved in our experiments is promising for electromagnetic applications of these materials. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Several studies are conducted to analyze the magnetic properties, magnetocaloric effect and the refrigerant capacity that is observed in the various Sr-doped [Eu.sub.8][Ga.sub.16][Ge.sub.30] type-I clathrates. These compounds are shown to be extremely beneficial for numerous cryogenic magnetic refrigeration applications.

The various effects of nanostructuring on the magnetocaloric effect observed in the Gd/W thin film heterostructures are determined. Nanostructuring is shown to be an extremely effective mode of modifying the magnetocaloric response of the materials.

Several analyses are conducted to explain the field dependence of the magnetic entropy change peak observed in the chemically-synthesized, monodispersed core-shell nanoparticles. The results demonstrate that the entropy and the position of the peak can be easily changed by manipulating the composition, as well as the nature of the shell and surfactant layers.

The magnetic properties of high quality Lu[Fe.sub.2][O.sub.2] single crystals grown by the floating zone method are studied. The analysis has shown that the multiple transitions are consistent with the picture of ferromagnetic clusters in the iron oxide planes with triangular lattice configuration favoring spin frustration and glass dynamics.

The particle blocking and carrier fluid freezing effects on the magnetization and relaxation processes in two different ferrofluids composed of [Fe.sub.3][O.sub.4] nanoparticles suspended in hexane and dodecane are analyzed by using the systematic dc and ac susceptibilities studies. Quantitative fits of the frequency dependent ac susceptibility to the Vogel-Fulcher model has shown that the blocking of magnetic nanoparticles in the frozen state has affected the interparticle dipole-dipole interaction, which has caused characteristic spin-glass-like dynamics.

Complex ac susceptibility measurements are described on composite Au-[Fe.sub.3][O.sub.4] nanoparticles of two different configurations, 'dumbbell' and 'flower' configurations. The Neel-Arrhenius model has failed to describe the blocking behavior of both types of particles and the Vogel-Fulcher model has fit the dumbbell particles indicating the importance of weak interparticle interactions in the system.

The magnetocaloric effect (MCE) properties in ball-milled Zn[Fe.sub.2][O.sub.4] particles are examined. The surface structure of zinc ferrite particles is sensitive to ball milling conditions and it is shown that these surface effects have a huge impact on the MCE.

Systematic demagnetization in polycrystalline [Eu.sub.8][Ga.sub.16][Ge.sub.30] clathrates were investigated in the temperature range of 0-3 T and change in temperature is calculated using the Maxwell relation from the family of M-H curves a different temperatures in the vicinity of the ferromagnetic Curie temperatures. The results reveal that clathrates, which are known to have the potential for excellent thermoelectric properties show promise as prospective magnetic refrigerant materials.

Quantum dots of InP:Mn are chemically prepared by following hot colloidal nanochemistry with starting precursors that obviate the need for external surfactant. Structural characteristics and analysis confirm that the magnetism in these quantum dots is not due to segregated binary MnP or MnO phases and that they truly represent a homogeneous dilute magnetic semiconductor.

Static and dynamic magnetic properties of cuboctahedrally truncated polydisperse, rf plasma torch synthesized NiZn ferrite nanoparticles is studied. The transmission electron microscopy determined nanoparticle size distribution is found to be log-normal.

The transport spin polarization is determined by making point-contact Andreev reflection (PCAR) measurement on bulk polycrystalline SrRu0.8Ti0.2O3 and SrRu0.92O3 samples. The measurements indicated that the SrRu0.8Ti0.2O3 system retains a high degree of spin polarization similar to the parent compound.

Temperature and field-dependent reversible transverse susceptibility (TS) measurements on a La(sub 0.85)Sr(sub 0.15)MnO3 single crystal at radio frequency using a reosnant tunnel-diode oscillator technique are performed. The TS experiments are demonstrated to be useful for studying magnetic anisotropy in the presence of structural and electronic transitions in the strongly coupled systems.

Multilayers of Ba(sub 0.5)Sr(sub 0.5)TiO3 [BSTO] and BaFe(sub 12)O(19) [BaM] are grown using magnetron sputtering on Al2O3 substrates. While the X-ray diffraction indicated that both BSTO and BaM were formed, the cross-sectional SEM studies showed sharp interfaces between BSTO and BaM layers.