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Research into transverse spin freezing in a-Fe(sub x)Zr(sub 100-x) and a-Fe(sub 90-x)Ru(sub x)Zr10 is presented. It was found that the basic form of the phase diagrams is consistent with current models, the decline in Tc is faster than anticipated.

A sample of an ordinary chondrite fall, Allegan, was shown by 57Fe Mossbauer spectroscopy to be unweathered. Using aerated deionized water at 25 [degrees] and 0 [degrees] C, and in one case with dissolved salts added, an attempt was made to simulate meteorite weathering processes in the hot and cold desert environments where these samples accumulate. The progress of artificial oxidation was monitored by 57Fe Mossbauer spectroscopy, and the final products were analyzed by neutron activation. The results confirm weathering mechanisms proposed for naturally weathered meteorites and suggest that temperature is the major factor controlling the stability of the observed oxide mineral assemblage. Akaganeite was observed as a major oxidation product in the experimentally weathered sample. This finding is interesting because it is widely accepted that [Beta]-FeOOH requires Cl- for stability: The sample weathered in deionized water showed only trace amounts of Cl- in both the fresh and weathered meteorite. We suggest that both Cl- and OH- may be effective in filling tunnel sites and that a complete solid solution is possible between these end-members. In addition, a calculated formation age of 4.59 [+ or -] 0.05 Ga and a cosmic-ray exposure age of 5.7-6.2 Ma, was derived from neutron activation analyses of the weathered sample. These ages are consistent with independent measurements made on samples of fresh Allegan, although small sample weights mean that the results should be treated with caution. However, the similar ages obtained in the weathered sample indicates that a wider spectrum of cosmochemical analyses is possible with weathered meteorites than previously thought and that congruent dissolution occurs during meteorite weathering.

Experimental and theoretical studies of rare-earth (R) iron-rich ternary intermetallic compounds show that they have a monoclinic structure and are of the form of R3(Fe,M)29. The monoclinic structure consists of 15 Fe(M) and two R sites. The 3:29 compounds exhibit good magnetic properties following their modification using N or H. The room-temperature coercivity of the compounds indicates that they are suitable for permanent-magnet applications.

The effects of Co or Ge doping on the magnetic decoupling behavior of nanocrystalline Fe89Zr7B3Cu1 are examined. The magnetic softness of Fe89Zr7B3Cu1 severely detiorates with the addition of Co due to induced anisotropy effect.

Zero-field muon spin relaxation (ZF-muSR) and selective excitation double Mossbauer (SEDM) spectroscopy were used for examining the spin dynamics in amorphous (a)-Fe90Sc10. A paramagnetic to spin-glass transition is observed in a-Fe90Sc10 at single transition of 105 K.

X-ray diffractrometry and Mossbauer spectroscopy is used to investigate the decomposition of the precursor amorphous phase in Nd5Fe(sub 77-x)B18Cr(sub x) (x=0 and 3), particularly Cr-induced Nd2Fe14B formation. Results show that amorphous Nd5Fe74Cr3B18 decomposes to stable alpha-Fe/Fe2B/NdFe4B4 through metastable Fe3B/Nd2Fe14B during isothermal annealing at 95 K. It is also shown that annealing treatment at 873 K spoils the metastable formation of magnetically hard Fe3B/Nd2Fe14B in the Cr-added system.

A study was conducted to analyze the magnetic characteristics of rhenium-doped a-Fe90Zr10 by magnetization, neutron depolarization, susceptibility, and Mossbauer spectroscopy. A magnetic phase diagram was presented. The C5 beamline of the Dualspec spectrometer was utilized to determine neutron depolarization. Experimental results indicated that rhenium leads to a very rapid loss of magnetic order.

A study was conducted to analyze the association between the mean hyperfine field of the residual intergranular amorphous phase and the coercivity in different nanocrystalline soft magnetic samples. The impact of spontaneous magnetization in the grain boundary area on their magnetic softness was examined. Results indicated variations in the exchange stiffness constant of the intergranular region.

The Be-substituted [Nd.sub.2]([Fe.sub.14-x][Be.sub.x])B compounds have been successfully prepared. The observed linear reduction of the unit cell volume with the Be substitution indicates that the Be atoms enter almost exclusively the Fe sites. Both the Curie temperature and magnetization are weakened upon the Be substitution; the reduction in [T.sub.C] is about 26K/Be atom and the reduction in the average Fe moment is about 0.26 [[Mu].sub.B]/Be atom, respectively. The fits to room temperature Mossbauer spectrum of [Nd.sub.2](Fe.sub.13]Be)B gives an average hyperfine field of 23.7 T. The room temperature anisotropy of Be substituted [Nd.sub.2]([Fe.sub.14-x][Be.sub.x])B compounds is around 8 T which is nearly unchanged, compared to the parent [Nd.sub.2][Fe.sub.14]B compound. Moreover, the Be substitution leads to an increase in the canting angle at 10 K, from 28 [degrees] to [approximately] 36 [degrees], and a decrease in the spin-reorientation temperature from 131 K to 123 for [Be.sub.0.5] and 112 K for [Be.sub.1.0] substitution, respectively. These effects indicate a weakened [A.sub.20] value and/or an enhanced [A.sub.40] value for Nd atoms.

A [Tb.sub.3][(Fe,V).sub.29] single crystal has been grown using the Czochralski method. Magnetization measurements along the hard axis of the crystal are presented. At low temperatures, a first-order magnetization process of type II occurs at large critical fields ([[Mu].sub.o][H.sub.c] = 10.6T at T = 5K). The data were analysed using the first-principle model in terms of exchange and crystal-field interactions. The second order crystal-field coefficients of two rare earth sites are estimated to be [A.sub.20] = 36K.[[a.sub.o].sup.-2] for the 41 site, and [A.sub.20] = +16K.[[a.sub.o].sup.-2] for the 2a site.

Thermogravimetric analysis and Mossbauer spectroscopic studies of the magnetic properties of Nd3(Fe,Ti)29 compounds subject to interstitial modification with C, H and N reveal that H addition enhances Tc but not iron moment, while N addition enhances both Tc and iron moment. Lattice expansion values for the maximum levels of six hydrogen and four nitrogen atoms per formula unit range from 2% to 6.5%. Carbon addition is not feasible due to the decomposition of the materials during reactions with C.