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A combination of Zr substitution and TiC addition has yielded adequate microstructural control in both the gas atomization (GA) and melt spinning (MS) methods and an [MRE.sub.2][(Fe, Co).sub.14]B alloy is developed with these modifications. The results have shown that the MS ribbon has a fine and uniform microstructure with an average size of 30 nm, whereas the GA spherical powder has an interior coarsened microstructure with a grain size of 80 nm and a rim area with a grain size of 10 nm.

Explorations in the metallurgical synthesis from the melt of bulk permanent magnets with coercivity conferred by the exchange bias mechanism are carried out in a two-phase materials system composed of ferromagnetic FeCo and antiferromagnetic, nominally equiatomic AuMn. Magnetization measurements of the composite confirm an exchange bias effect correlated with a coercivity increase over that of the (Fe,Co) melt-spun base alloy.

High-energy synchrotron radiation and Debye-Scherrer geometry were used for performing a series of high temperature x-ray diffraction (HTXRD) experiments on rapidly-solidified Nd2Fe14B alloys from room temperature to 1073 K. The unit cell volume for Nd2Fe14B contracted primarily due to the contraction in the basal plane from room temperature up to the Curie temperature.

Metal-bonded cobalt ferrite composites are promising candidates for torque sensors and other magnetostrictive sensing and actuating applications. The temperature dependences are explained by the changes of magnetostriction, anisotropy, spontaneous magnetization, and pinning of domain walls caused by the availability of increased thermal energy.

Six elements were added to the base Nd2Fe14B (2-14-1) composition to reduce its sensitivity to localized changes in cooling rate and control grain growth through crystallization. It is shown that the modified alloy leads to uniform hard magnetic properties over a wide range of cooling rates. The improvements in the magnetic properties and the bulk method used to characterize microstructural inhomogeneities based on loop shape are discussed.

The local electronic and chemical environment of TiC-modified Nd2Fe14B ribbons are studied using positron annihilation spectroscopy. Results show that higher concentration of alloying additions increases the shape parameter, S, of the symmetric Doppler-broadened positron-electron annihilation peak. This increase in S can be considered an increase in the amount of open volume in the quenched glass.

It has been shown that the addition of excess Fe and B improves the exchange coupling effect in Nd-Fe-B alloys. TiC additions have been show to improve quenchability and inhibit grain growth during annealing. The effects of TiC addition on a high remanence alloy Nd(sub9.5)Fe(sub84.5)B(sub6), was undertaken to determine whether addition gives better quenchability and microstructural control in subsequent annealing processes.

Several magnetic measurements and electron microprobe analyses are conducted to explain the microstructures, as well as the magnetic properties of the various sintered MR[E.sub.2][Fe.sub.14]B magnets (MRE = Y+Dy+Nd). Composition segregation of grains is shown to lead to the higher temperature coefficients in these magnets.

The reaction path for the preparation of LaFeAsO and LaFeAs[O.sub.1-x][F.sub.y] by solid state reaction is analyzed by in situ height temperature x-ray diffraction method and differential thermal analysis. The formation of LaFeAsO based phase is resolved above 800 [degree]C and the reaction pathways and the difference between F-free and F-doped samples are discussed.

The role of chemical ordering and annealing in fine-tuning the magnetostructural properties of [Ni.sub.50][Mn.sub.50-x][Sn.sub.x] (x=10-25) is examined. The results have shown that the martensitic transformation has occurred only in those compositions where the single phase [L2.sub.1] is retained in a metastable state on cooling.

Gas atomization powder with Zr substitutions for the MRE and ZrC additions are analyzed. The results have shown that the partial substitutions of Zr and the ZrC additions have improved the glass formability in the alloys and the magnetic properties of the annealed powder have varied with particle size.

The devitrification behavior of nanocrystalline MR[E.sub.2][(Fe,Co).sub.14]B+ZrC (MRE=Nd+Y+Dy) is analyzed by using differential scanning calorimetry (DSC) and analytical transmission electron microscopy (TEM) methods. The partitioning behavior of various elements at different annealing conditions is associated with changes in magnetic properties, which has led to an improved optimum microstructure.

The effect of particle size on magnetic properties in single-crystalline multiferroic Y[Mn.sub.2][O.sub.5.07] nanoparticles is examined. The ferromagnetic-like phase is attributed to the surface layer of the nanoparticles and the broad magnetic transition is caused by the dispersion of particle size and the size dependence of the transition temperature.

The magnetostriction and microstructure of Fe-Ge are examined to correlate magnetostriction with microstructure. The analysis has shown that the changes of the magnetostriction with Ge additions are correlated with the structural changes in Fe-Ge alloys.

BiFe[O.sub.3] and PbTi[O.sub.3] are used on a Sc-modified Pb([Fe.sub.2/3][W.sub.1/3])[O.sub.3] compound with strong cation order in order to enhance the multiferroic properties. BiFe[O.sub.3] is selected due to its multiferroism and large ferroelectric remanent polarization and PbTi[O.sub.3] is selected due to its high ferroelectric transition temperature and its ability to stabilize the perovskite phase.

The partitioning behavior of various rare-earth (RE) elements during solidification and their segregation behavior at the grain boundaries are investigated in nanocrystalline alloys by transmission electron microscopy and atom probe tomography. The Y:(Dy+Nd) ratio in the Y-Nd-Dy alloy is lower than its nominal compoistion, indicating that the Y is segregating to grain boundaries or forming a second phase.

The effect of Zr substitution on the microstructure and magnetic properties in [Nd0.5(YDy)0.25](sub 2.2-x)Zr(sub x)Co(sub 1.5)Fe(12.5)B ribbons melt spun at a wheel speed of 10 m/s is studied. The results revealed that Zr substitution for R could significantly refine the grain size in as-spun [Nd0.5(YDy)0.25](sub 2.2-x)Zr(sub x)Co(sub 1.5)Fe(12.5)B ribbons.

The thermal expansion and Gruneisen parameter of polycrystalline 'Pr5Ni2Si3' and 'Pr15Ni7Si10' are investigated over the temperature range of 5-300 K. Results show two magnetic transitions in each compound, the higher temperature transition corresponding to the Curie temperature and the lower temperature transition resulting from a spin reorientation.

The report presents the temperature dependence of the magnetic anisotropy and magnestostriction in the region of anomalous magnetostriction peaks. It relates the results to a magnetization dependence model.

The atomic positions and the bond distances are measured from 300 to 1000 K using synchrotron x-ray diffraction in order to determine the Fe-Fe and R-Fe interactions that give rise to the Invar effect. The bonds between Fe(j2) and its neighboring sites have relatively larger magnetostrictions than most other bonds explaining the larger alpha-axis magnetorestriction in these compounds and the iron sublattices dominate the spontaneous volumetric magnetostriction of Y2Fe14B and Nd2Fe14B compounds.

The processing induced changes of the Curie temperature (C(sub c)) in melt-spun ribbons of Nd2Fe14B with alpha-Fe in relation to their anomalous thermal expansion are reported. The d spacing of the (110) of alpha-Fe and (006) of 2-14-a indicates that changes in T(sub c) may be due to epitaxial stresses affecting the exchange coupling in the nanocomposite alloys.

The high hysteresis in a rapidly solidified Tb-Al alloy that has been structurally characterized is reported. The measured single-phase loop shapes and the development of high coercivity in the homogeneous metallic glass state is explained by an exchange bias mechanism that results in a near perfect distribution of fragile pinning centers.

TiC additions to Nd(sub 2)Fe(sub 14)B have shown to enhance the control of microstructure and greatly modify the solidification behavior of the alloy. The activation energy for crystallization, the crystallization enthalpy, and temperature dependent crystallization rates are determined.

Elevated-temperature superconducting quantum interference device magnetometry was employed to investigate the detailed phase constitution of nominally glassy stoichiometric Nd(sub 2)Fe(sub 14 )B melt-spun ribbons modified with 6 wt % Ti/C. Analysis of the distribution and size of the alpha-Fe clusters provides insight into the nucleation and growth process that produces the crystallized microstructure associated with high energy-product melt-spun Nd(sub 2)Fe(sub 14)B based magnets.