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Fe-based amorphous alloys in Fe- (Al, Ga)-(P,B,C, Si) system were found to exhibit a wide supercooled liquid region exceeding 50 K before crystallization. The high stability of the supercooled liquid enabled the production of cylindrical bulk amorphous alloys with diameters up to 2 mm by copper mold casting. The Fe-based bulk amorphous alloys exhibit ferromagnetism with the Curie temperature of about 600 K. The saturation magnetization (Bs), coercivity (Hc) and permeability ([[micro].sub.c]) at 1 kHz in as-quenched state are 1.07 T, 12.7 A/m and 3600, respectively, for [Fe.sub.73][Al.sub.5][Ga.sub.2][P.sub.11][C.sub.5][B.sub.4] and 1.14 T, 0.5 A/m and 3200, respectively for [Fe.sub.71][Al.sub.5][Ga.sub.2][P.sub.10][C.sub.6][B.sub.4][Si.sub.1]. Besides, the use of the Fe-based amorphous alloys enabled the production of thick amorphous ribbons above 100 [[micro]meter] in thickness and the thick samples also exhibit good soft magnetic properties. The success of synthesizing the bulk Fe-based amorphous alloys with good soft magnetic properties is promising for future development as a new type of soft magnetic materials.

A solid-state phase transformation (SSPT) is observed in nanocrystalline [Sm.sub.2][Fe.sub.17][C.sub.x], x=0-1 ([Th.sub.2][Zn.sub.17]-type carbides) prepared by both ball milling and rapid solidification. Upon annealing at 800 [degrees] C the [Sm.sub.2][Fe.sub.14]C ([Nd.sub.2][Fe.sub.14]B-type) phase is formed for x [greater than or equal to] 0.3. For x between 0.3 and 1.0, the [Sm.sub.2][Fe.sub.17][C.sub.y] (y [similar to] 0.3) and [Sm.sub.2][Fe.sub.14]C phases co-exist. The process of the SSPT to [Sm.sub.2][Fe.sub.14] is faster in finer-grain samples. The annealing time required for a complete transformation varies from 15 min for a sample with an average grain size of 40 nm to 28 h for a 200 nm grain size sample. These results suggest that the SSPT is made accessible by reducing the grain sizes. Studies on [Nd.sub.2][Fe.sub.17][C.sub.1.0] show that certain [Nd.sub.2][Fe.sub.14]C powders synthesized through SSPT contain highly anisotropic particles, suggesting a promising technique to produce anisotropic [Nd.sub.2][Fe.sub.14]B-type permanent magnets.

The magnetic property of supersaturated [Fe.sub.20][Co.sub.30][Cu.sub.50] solid solution, prepared by mechanical alloying, has been investigated by using magnetometry, Mossbauer spectroscopy and inelastic neutron scattering measurements. Magnetization measurement of the alloy could be analysed by ferromagnetism only. However, Mossbauer spectroscopy and inelastic neutron scattering experiment showed that not only ferromagnetic phase but also paramagnetic phase of about 12% coexist in the alloy. Spin wave stiffness constant obtained from the analysis of the temperature dependence of magnetization was similar to the value obtained from analysis of inelastic neutron scattering experiment.

The alloys with chemical compositions of [Nd.sub.16][Fe.sub.76-x] [B.sub.8][Zr.sub.x] (x = 0, 0.1) have been HDDR processed, and the magnetic properties and anisotropy of the HDDR material have been characterised by means of VSM measurements using a magnetically aligned sample. Anisotropy of the HDDR powder material has been evaluated by comparing the remanence values of the aligned sample measured along the aligning direction and the direction perpendicular to it. It has been found that the intrinsic coercivity of the HDDR powder strongly depends on the particle size of the powder. As the particle size decreases, the intrinsic coercivity decreases radically, and this is explained in terms of structural damage induced in the particle during mechanical milling. It has also been found that the degree of alignment representing the anisotropy of the HDDR powder is enhanced with decreasing particle size. Some degree of alignment has also been observed in the HDDR material obtained from the Zr-free Nd-Fe-B-type alloy, and this may possibly be attributed to either incomplete disproportionation, excess grain growth of the recombined grains or the presence of very fine particles as a result of milling.

We have carried out neutron and magnetic studies on [Nd.sub.2][Fe.sub.17-x][T.sub.x] (T=Si, Mn) alloys. The unit cell of the compounds contracts with both Si and Mn substitution. Si atoms avoid the 6c site, prefer the 18h site strongly, fill the 9d site steadily and fill the 18f site only at relatively high Si concentration. Mn atoms avoid the 9d sites but prefer the 6c site strongly, while the 18f site and 18h site fill slowly. The Si site occupancies appear to be dominated by the crystal environment while the Mn site occupancies are dominated by steric considerations. The Curie temperature of the compound [Nd.sub.2][Fe.sub.17] increases significantly with Si substitution but is only affected slightly by the Mn substitution. Although the unit cell contracts with increasing Si concentration, the average length of bonds to the Fe(6c) and the Fe(18f) sites increase slightly at x

The magnetic properties, phases transformations and microstructural evolution of [Nd.sub.9.5][Fe.sub.85.1-x][B.sub.5+x](x=0, 1, 3 and 4) alloy ribbons have been investigated. Excellent magnetic properties with a Br=11.7 kG, iHc=6.6 kOe, (BH)max=18.7 MGOe and Br=11.4 kG, iHc=6.3 kOe, (BH)max=19 MGOe, can be achieved in the alloys with x=0 and 1, respectively, simply from direct quenching. For alloy ribbons with higher boron content (x=3 and 4), the magnetic properties degrade and are lower than that of the former even after subsequent annealing. From x-ray diffraction, TEM and magnetic analysis, the degradation of magnetic properties was found to result from the formation of [Fe.sub.3]B phase inside [Nd.sub.2][Fe.sub.14]B and [Alpha]-Fe phases and to grain coarsening leading to the reduction of the exchange coupling effect between [Nd.sub.2][Fe.sub.14]B and [Alpha]-Fe or [Fe.sub.3]B phases.

The crystallization behavior of [Nd.sub.x][Fe.sub.93-x][Nb.sub.1][B.sub.6] melt-spun ribbons was investigated using calorimetric techniques. The crystallization products were identified by X-ray diffraction and thermomagnetic measurements. Samples with x [greater than or equal to] 10 crystallize directly from amorphous to a mixture of [Nd.sub.2][Fe.sub.14]B and [Alpha]-Fe phases. For 10 < x

High-coercivity Sm[Co.sub.x] alloys were prepared by melt spinning. X-ray diffraction data indicate that the alloys exhibit a single phase Sm[Co.sub.5] and [Sm.sub.2][Co.sub.17] structure at x = 5.0 and x = 8.5, respectively. A two-phase structure appears at 5.0 < x < 8.5. The coercivity of the studied alloys increases as the wheel speed is increased up to a maximum value of 40 m/s. The grain sizes of the as-spun alloys were measured to be 0.1-1.0 [[micro]meter]. The high coercivity of the microcomposite alloys can be explained from the unpinning of domain walls at nucleation sites.

[Y.sub.2][Fe.sub.15][T.sub.2]C (T=Al,Ga,Si) crystallize in the rhombohedral [Th.sub.2][Zn.sub.17]-type structure. The refined compositions are in excellent agreement with that of the nominal ones. The site occupancies of the substitutional atoms, (Al, Ga and Si) are found to be similar to those of the corresponding uncarbided compounds and not changed by the C atoms. That is, Al, Ga and Si all profer the 18h site at the present substituent content, which appears to be determined by the site environments since the 18h site has the highest number (3) of rare earth neighbors in the structure. C atoms are found to occupy the octahedral interstitial 9e site (1/2, 0, 0) which has two rare earth neighbors and four Fe/T neighbors, in all three samples. The Curie temperatures have been measured to be 588K, 515K, and 535K for the Ga, Al, and Si samples respectively.

The magnetic and structural properties of Sm[Co.sub.2][Fe.sub.2]B powders prepared by ball milling, mechanical alloying and melt-spinning have been studied. Sm[Co.sub.2][Fe.sub.2]B powders milled for 5 minutes and then aligned were found to be anisotropic by x-ray diffraction. An optimum coercivity of, Hc = 13.5 kOe, was obtained after milling for 120 minutes corresponding to a particle size in the ranges of 1-6 [[micro]meter]. Mechanically alloyed powders were shown to have the highest coercivity, 16 kOe, after heat-treating at 600 [degrees] C for 30 minutes. The melt-spun samples had a low coercivity due to an unidentified phase possibly with low anisotropy.

Nanocrystalline structures were obtained by a rapid thermal annealing (RTA) process with a heating rate of 600 [degrees] C/min for a soaking time of 2 minutes for melt-spun [Nd.sub.6][Fe.sub.88]-xMx[B.sub.6] amorphous alloys (M = Ti or V, x = 0 [similar to] 5). Exchange coupling interaction between the magnetically hard and soft phases was studied with the [Delta]M plots. Addition of Ti or V to replace iron is effective in increasing remanence ratio, Mr/[M.sub.2T], and energy product of the modified alloys, especially that modified by V, although both saturation magnetization and remanence are decreased due to magnetic dilution. High resolution TEM studies showed that both Ti and V is effective in refining grain size of both hard and soft phases to 20 [similar to] 23 nm compared with 50 [similar to] 52 nm for the x = 0 alloy. The substitution with V results in a decrease in coercivity despite of refined grains.

Four samples of [Nd.sub.2][Fe.sub.17-x][M.sub.x][C.sub.y] (where M = Al, Ga, Ti, V) were synthesized using rf induction melting and C was introduced from the melt. Structural studies were then carried out using neutron diffraction. All samples were confirmed to have the [Th.sub.2][Zn.sub.17]-type rhombohedral structure with expanded unit cell volumes. However, the volume effect, as well as the site preference of the substitutionai atoms (M) is different among these samples and is different compared to their uncarbided counterparts. The C atoms were found to reside in the 9e site for all samples. The observed Curie temperature is higher for samples with higher C concentrations.