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A new analysis approach is developed for evaluating the atomic ordering in full-Heusler alloys, which is extension of the commonly used Webster model. The model is applied to full-Heusler [Co.sub.2]FeSi alloy thin films formed by rapid thermal annealing.

The magnetoresistance and the Hall effect in the [Fe.sub.3][O.sub.4]-Si[O.sub.2]-Si structure is described. The results have confirmed that the large magnetoresistance at 230 K has originated from the amplification of the magnetoresistance of the magnetite in the [Fe.sub.3][O.sub.4]-Si[O.sub.2]-Si structure.

The magnetic properties and magnetocaloric effect of amorphous alloys [Ce.sub.2][Fe.sub.23-x][Mn.sub.x][B.sub.3] are examined. The spin glass (SG) behavior in amorphous alloy [Ce.sub.2][Fe.sub.23-x][Mn.sub.x][B.sub.3] is attributed to the disordered structure resulting from their amorphous nature and the competition between the Fe-Fe ferromagnetic (FM) coupling and Fe-Mn antiferromagnetic (AFM) negative coupling.

Rapidly solidified [Ni.sub.54][Fe.sub.27-2x][Ga.sub.19+2x] ferromagnetic shape memory alloys are made by melt-spinning with variation of Fe and Ga contents in order to describe the martensitic phase transformation, microstructures and magnetic properties. The microstructures of the as-spun ribbons have displayed a gradual transition from cellular to dendritic structure with increasing Ga concentration and with the presence of some internal martensitic twin bands at higher Ga content.

Thermomagnetic properties of off-stoichiometric [Ni.sub.54][Fe.sub.19][Ga.sub.27] Heusler alloys are measured by using differential scanning calorimeter employing Peltier cells. Direct measurement and Clausius-Clapeyron equation have shown that the effect of the magnetic field is a shift of transition temperatures of 0.2 K[T.sup.-1].

The growth, structural characterization and magnetic properties of ferromagnetic [Fe.sub.0.8][Ga.sub.0.2] nanowires that are grown on quartz substrates by electrospinning are described. The nanowires have displayed a large coercivity at 4 K in the parallel field and hysteresis loops are measured with magnetic field applied perpendicular and parallel to the substrate plane at 4 and 300 K.

The magnetocaloric effects (MCEs) of La[Fe.sub.13-x][Si.sub.x] compounds doped by magnetic rare earths (R = Ce, Pr and Nd) and transition metal (Co) are studied. The analyses have shown that refrigerants made of La[Fe.sub.13-x][Si.sub.x] have as low as possible Si content and proper Co content simultaneously.

The magnetic transition is analyzed in [Mn.sub.1.1][Fe.sub.0.9][P.sub.0.8][Ge.sub.0.2] by using magnetic measurements and [super 57]Fe Mossbauer spectrometry. The results have shown that the magnetic transition at [T.sub.C] is first order and has suggested that there is an additional irreversible magnetostructual change during the first cooling process of the as-prepared sample.

Magnetic and magnetocaloric properties of single crystal [Er.sub.2][([Co.sub.0.4][Fe.sub.0.6]).sub.17] are examined. First order spin reorientation phase transition is observed at 272 K, magnetic easy-axis anisotropy is below this temperature and the easy-plane one above.

The magnetic properties, magnetic entropy change and hysteresis loss in La[Fe.sub.11.7][([Si.sub.1-x][Cu.sub.x]).sub.1.3] compounds are examined. The compounds have retained the cubic Na[Zn.sub.13] structure when the substitution of Cu has reached 20%, which has also reduced both thermal and magnetic hysteresis.

The magnetocaloric effect (MCE) of the amorphous Fe-Zr-B-M (M = Mn, Cr and Co) ribbons is examined. The field dependence of the magnetic entropy change has displayed power dependence for the specimens and in the ferromagnetic range the exponent is close to 1, whereas in the paramagnetic regime the exponent is 2, which has agreed with the Curie-Weiss law.

The first-order antiferromagnetic/ferromagnetic phase transition in ordered Fe[Rh.sub.100-x][Pt.sub.x] thin films grown onto MgO(100) substrate is examined by temperature dependent magnetization measurements. The entropy changes associated with the magnetic phase transition are analyzed and it is shown that the change in the electronic entropy associated with the magnetic moment of Rh atoms is the main mechanism for the first-order magnetic phase transition in ordered FeRh-based alloys.

FePt nanocrystals are prepared by simultaneous reduction of platinum acetylacetonate and thermal decomposition of iron pentacarbonyl in solvents/surfactants and the shape control is realized by varying synthesis parameters. The as-synthesized FePt nanocrystals are transformed to the chemically ordered [L1.sub.0] structure upon heat treatment, which has displayed hard magnetic properties with coercivity as high as 25 kOe.

The antiferromagnetic state seen in [Lu.sub.2][Fe.sub.17] at elevated temperatures is stabilized down to the ground state in [([Lu.sub.0.8][Ce.sub.0.2]).sub.2][Fe.sub.17] and [Lu.sub.2][Fe.sub.16.5][Ru.sub.0.5]. The pressure and substitution effects are understood in terms of exchange interaction varying with changes in the lattice parameter c for [([Lu.sub.0.8][Ce.sub.0.2]).sub.2][Fe.sub.17], while for [Lu.sub.2][Fe.sub.16.5][Ru.sub.0.5], the change in magnetic structure has occurred due to the weakening of the positive exchange interaction as a result of the reduction in the Fe magnetic moments.

The effect of B content on the magnetic properties, phase evolution, magnetic after effect and the activation energy for the melt-spun [[([Fe.sub.0.7][Co.sub.0.3]).sub.0.725][Pt.sub.0.275]].sub.100-x][B.sub.x] ribbons is examined. Sufficient amount of boron addition has decreased the activation energy of ordering transformation and has refined the grain size of the ribbons after thermal annealing.

Neutron diffraction patterns are acquired in situ from a melt-spun amorphous [Fe.sub.74][Nd.sub.5][B.sub.18][Cr.sub.3] alloy upon rapid thermal annealing at constant rates. The heterogeneous nucleation of [Nd.sub.2][Fe.sub.14]B on tetragonal-[Fe.sub.3]B precipitates promoted by the 3d transition-metal additives is used for magnetic hardening.

[L1.sub.0] FePt-[Ta.sub.2][O.sub.5] films with (001) texture are prepared by cosputtering FePt and [Ta.sub.2][O.sub.3] targets and in situ heated at 350 [degree] C. Well-isolated FePt grains of tall column structures are seen for the 12 nm thick FePt film when doped with 20 vol % and these films with large coercivity are used for perpendicular recording applications.

Bulk nanocrystalline magnets are prepared by using mechanical alloying and hot compaction, whose compositions are Sm[([Co.sub.1-x][Fe.sub.x]).sub.z] and Sm[[([Co.sub.1-x][Fe.sub.x]).sub.1-y][F.sub.y]].sub.z]. The coercivity has decreased, but it is good for the material with up to 35% of soft phase, showing evidence of exchange coupling and the analyzed have shown hard phase and Fe-Co soft phase coexisting in the specimens with z>8.5.

The synthesis of the [Sm.sub.5][Fe.sub.7] phase and its magnetic properties are described. The [Sm.sub.5][Fe.sub.17] phase is produced by the annealing of a Sm-Fe melt-spun ribbon and the coercivity of the annealed melt-spun ribbon is highly dependent on both the annealing temperature and Sm content of the Sm-Fe alloy.

Spark plasma sintering method is used for studying the structure and magnetic properties for Sm[([Co.sub.0.74][Cu.sub.0.12][Fe.sub.0.1][Zr.sub.0.04]).sub.7.6] nanocrystalline ball milled powders and bulk magnet. The coercivity of the powders has decreased as the annealed temperature has increased and the Mr/Mn ratio of 0.63 has shown the existence of intergrain exchange coupling among the nanograins.

An amorphous [Fe.sub.73.5][Cu.sub.1][Nb.sub.3][Si.sub.15.5][B.sub.7] ribbon is pulse annealed continuously under tensile stress for preparing a nanocrystallized toroidal core with controlled permeability. The results have shown that the continuous stress annealing by pulse annealing method is one of the methods for preparing a long ribbon with excellent magnetic properties.

The soft magnetic property and the structure of the new type nanocrystalline Fe-(P,B,Si,Nb,Cu) alloy with high Fe content are examined. [Fe.sub.77.9][P.sub.3][B.sub.14][Nb.sub.5][Cu.ub.0.1] alloy has a supercooled liquid region of 33 K defined by the difference between the glass transition temperature and crystallization temperature, which is related to the high glass-forming ability leading a thickness of 140 [micro]m melt-spun ribbon with a glassy phase.

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.

Varying amounts of boron are added to the host FeGa alloy in order examine its affect on the local atomic structure and magnetic and microwave properties. The extended x-ray absorption fine structure (EXAFS) fitting results have shown a contraction of lattice parameters with the introduction of B and the Debye-Waller factor has increased as a function of boron addition.

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.

Magnetic properties and magnetocaloric effect of GdFeAl compound are examined. A large refrigerant capacity is obtained due to the large full width at half peak of the magnetic entropy change versus temperature curve in GdFeAl compound.

Direct isothermal annealing and a heating rate of 25 [degree]C/h are used for obtaining final {110} grains. The results are described in terms of the segregation kinetics of sulfur affected by heating rate and the grain boundary pinning effect of the segregated sulfur.

The high temperature coercive field behavior of [Fe.sub.80][Zr.sub.20] nanocrystalline alloy powder having two-phase microstructure prepared by mechanical alloying process is examined. The temperature dependent coercive field behavior is attributed to the variations in both the effective anisotropy and the exchange stiffness constant with temperature.

The effect of cobalt doping on the thermopower of the superconductor FeSe is examined through electrical and thermal transport measurements. The results have shown the destruction of superconductivity at very low Co concentrations and thermopower data has shown negative charge carriers along with a large enhancement of the Seebeck coefficient.

The magnetic and structural properties of [L1.sub.0]-FePt thin films, prepared via molecular beam epitaxy directly onto MgO(001) substrates, are studied. The effect of elevated substrate temperatures and postgrowth high temperature annealing on the structural and magnetic properties is examined.

Thin films of LaMnXO (X = P, As and Sb), which are isostructural compounds of the newly discovered superconductor, LaFeAsO, are grown epitaxially on MgO (001) substrates by pulsed laser deposition. Thermopower and optical absorption measurements have shown that all the films are p-type semiconductors with indirect bandgaps, which are supported by density functional calculations with the GGA+U approximation.

The effect of the deposition pressure (P[O.sub.2]) and substrate temperature ([T.sub.S]) during the growth of [Bi.sub.2]FeCr[O.sub.6] thin films grown by pulsed laser deposition is examined. Polarization measurements at room temperature have shown that [Bi.sub.2]FeCr[O.sub.6] films have excellent ferroelectric properties with ferroelectric hysteresis loops displaying a high remanent polarization along the pseudocubic [001] direction.

Metal flux synthesis in a low-melting eutectic mixture of lanthanum and nickel has produced a family of complex intermetallic carbide phases, [La.sub.21][Fe.sub.8][M.sub.7][C.sub.12] (M = Sn, Bi, Sb, Te, Ge), having tetrahedral structure. The AC susceptibility data has shown that the temperature of the transition is frequency-dependent, which is characteristic of spin glass systems.

The measurements of the X-ray powder diffraction pattern at hydrostatic pressures of up to 17 GPa applied by a He gas pressure medium in a diamond anvil cell have shown a bulk modulus for LiFeAs of 57.3(6) GPa that is much smaller than that of other layered arsenide and oxyarsenide superconductors. The decrease in superconducting transition temperatures ([T.sub.c]) with applied pressure is consistent with observations of the iron arsenides and related materials.

Nanostructured BiFe[O.sub.3] particles are prepared by a hydrothermal method and the effects of particle size on photocatalytic activity and magnetic property of BiFe[O.sub.3] are examined. The optical absorption spectra have shown that the band-gap energy has increased with decreasing crystalline size due to the quantum size effect.

Temperature dependent impedance measurements are carried out on chemical solution deposition BiFe[O.sub.3] thin films on Pt/Si substrates. X-ray diffraction analysis has displayed the presence of predominantly single phase BiFe[O.sub.3] and the grain and grain boundary conductivity activation energies are estimated.

Magnetic entropy change and refrigerant capacity of Gd-based amorphous [Gd.sub.71][Fe.sub.3][Al.sub.26] and [Gd.sub.65][Fe.sub.20][Al.sub.15] alloys are examined. A very large refrigerant capacity and magnetic entropy change have made them good candidates for magnetic refrigerant.

The structure, thermal stability and crystalline behavior of [([Fe.sub.0.9][Co.sub.0.1]).sub.67.5][Nb.sub.4][Gd.sub.3.5][B.sub.25] glassy alloy, displaying a two-stage-like glass transition phenomenon, are examined by using x-ray diffraction, transmission electron microscopy and differential scanning calorimetry. This glassy alloy has displayed high glass-forming ability, enabling the formation of glassy alloy rods with diameters exceeding 3.0 mm, high saturation magnetization, low coercive force and high fracture strength.

Fe-Ni based amorphous thin films are prepared by thermal evaporation and glancing angle x-ray diffraction studies have showed that the irradiated films retain their amorphous nature. Magnetic measurements using a vibrating sample magnetometer has displayed that the coercivity of the films has increased with an increase in the ion fluence and the ability to modify the magnetic properties via swift heavy ion (SHI) irradiation is used for applications in thin film magnetism.

The hyperthermia measurements on a colloidal solution of 14.2(plusminus)1.5 nm monodisperse FeCo nanoparticles (NPs) is reported. The hyperthermia measurement provide insight into the frequency dependence of the coercive field which is quantitative agreement with a simple model of noninteracting NPs.

The magnetocaloric properties of powder samples of the monoclinic Y[Fe.sub.2][H.sub.4.2], Y[Fe.sub.2][D.sub.4.2] and [Y.sub.0.5][Tb.sub.0.5][Fe.sub.2][D.sub.4.2] compounds are analyzed at their itinerant electron metamagnetic transition. Large reversible entropy changes have made the alloys as good candidates for magnetic refrigeration applications and the results are compared to previous data on other potential magnetic refrigerants with itinerant electron metamagnetic transitions.

The effect of the substitution of P for B and Cu for Fe on the structure and magnetic properties of melt-spun [Fe.sub.82][Si.sub.9][B.sub.9] alloys with higher Fe content is examined. Fe-rich [Fe.sub.81.7][Si.sub.9][B.sub.7][P.sub.2][Cu.sub.0.3] heteroamorphous alloy with an as-quenched structure consisting of extremely small [alpha]-Fe-like clusters has displayed the lower coercivity and the higher saturation magnetization than the typical Fe-based monolith amorphous alloy at an as-quenched state.

Ab initio molecular dynamics simulation is used for studying the structures of [Fe.sub.78][M.sub.9][B.sub.13] (M=Nb, Si, and Zr) melts. The structural and dynamical properties of these melts have changed with different M elements and the degree of complexity of molten structure caused by the interactions among Fe, M and B has played a vital role in their glass forming ability.

The changes in the structure with thermal history and their correlation with the observed magnetostriction values in Fe-Ga, Fe-W and Fe-Mo single crystals are examined. The analysis of the high-resolution x-ray diffraction (XRD) patterns has suggested that the changes in magnetostriction with composition and thermal history are related to the local strain modulations associated with the solutes, short range order, long range ordered coherent second phases, and other structural defects.

The effect of metalloids composition in Fe-Pt-metalloids alloys on the glass-forming ability is explored to develop [Fe.sub.55][Pt.sub.25][Si.sub.16][B.sub.2][P.sub.2], [Fe.sub.55][Pt.sub.25][Si.sub.15][B.sub.3][P.sub.2] and [([Fe.sub.0.55][Pt.sub.0.25][Si.sub.0.16][B.sub.0.02][P.sub.0.02]).sub.96][Zr.sub.4] (at%) glassy alloys with [DELTA][T.sub.x] of 37 K and 48 K, respectively. These Fe-Pt-based glassy alloys are found to have great potential for fabrication of hard magnetic micro/nano structures due to their high magnetocrystalline anisotropy of the [L1.sub.0] phase.

The magnetization of Fe/Si multilayers, grown by thermal evaporation in an ultrahigh vacuum system, is examined at high temperatures. A quantitative analysis of the irreversible behavior is described in terms of an exponential diffusion-like kinetic equation for the reaction that has produced the Fe-Si nonmagnetic phase.

The resistivity and magnetization measurements on nearly stoichiometric [Fe.sub.3]Si films epitaxially grown on GaAs substrates by electron-beam evaporation in an ultrahigh vacuum chamber are described. The hysteresis loops have shown that the samples are ferromagnetic at room temperature.

The pressure dependence of the growth of [alpha]-Fe and [Nd.sub.2][Fe.sub.14]B nanocrystals in amorphous [Nd.sub.9][Fe.sub.85][B.sub.6] is measured. The studies have shown that the growth of nanocrystals is dependent on atomic diffusion mediated by vacancy-type thermal defects.

A pump-probe optical technique, time-domain probe-beam deflection (TD-PBD), is described that has enabled the measurements of the coefficient of thermal expansion (CTE) with micron-scale spatial resolution. The studies have shown the usefulness of TD-PBD for high-throughput CTE measurements by applications on a Fe-Ni diffusion couple and the dentin-enamel junction in a human tooth.

A series of FePt nanoparticles is prepared by the thermal decomposition of iron pentacarbonyl and reduction in platinum acetylacetone in phenyl ether solvent. The studies have shown that the compositional variability is a result of the slow kinetics of iron pentacarbonyl's decomposition in the reaction.