Method of preparing a magnetic material

A method of forming a magnetic material. The magnetic material is a solid mass of grains, and has magnetic parameters characterized by: (1) a maximum magnetic energy product, (BH).sub.max, greater than 15 megagaussoersteds; and (2) a remanence greater than 8 kilogauss. The magnetic material is prepared by a two step solidification, heat treatment process. The solidification process is carried out by: (a) forming a solution of reducible precursor compounds of the magnetic material; and (b) thereafter reducing the reducible, precursor compounds and forming a precipitate thereof. The precipitate has a morphology characterized as being one or more of (i) amorphous, (ii) microcrystalline, or (iii) polycrystalline. The grains within the precipitate have, at this stage of the process, an average grain characteristic dimension less than that of the heat treated magnetic material. In the second, or heat treating, stage of the process, the precipitated solid is heat treated to form a solid material comprised of grains meeting at grain boundaries. The grains and grain boundaries have the morphology of the magnetic material.

FIELD OF THE INVENTION 
The invention relates to permanent magnetic alloy materials and methods of 
preparing them. 
BACKGROUND OF THE INVENTION 
There has long been a need for a relatively inexpensive, strong, high 
performance, permanent magnet. Such high performance permanent magnets 
would be characterized by relatively high magnetic parameters, e.g. 
coercive force (H.sub.c) or coercivity, remanent magnetization or 
remanence, and maximum energy product. 
Moreover, an ideal high-performance permanent magnet should exhibit a 
square magnetic hysteresis loop. That is, upon application of an applied 
magnetic field H greater than the coercive force Hc, all of the 
microscopic magnetic moments should align parallel to the direction of the 
applied force to achieve the saturation magnetization Ms. Moreover, this 
alignment must be retained not only for H=0 (the remanent magnetization 
Mr), but also for a reverse applied magnetic force of magnitude less than 
Hc. This would correspond to a maximum magnetic energy product (the 
maximum negative value of BH) of 
EQU (Mr.sup.2 /4)=(Ms.sup.2 /4) 
Unfortunately, this ideal situation is at best metastable with respect to 
the formation of magnetic domains in other directions, which act to reduce 
Mr and BH.sub.max. 
Conventional high-performance permanent magnets that approach square-loop 
behavior have four general requirements: 
1. The material must be composed primarily of a ferromagnetic element or 
compound with a Curie temperature Tc that significantly exceeds the 
application temperature Ta, and with Ms at Ta large. Practically speaking, 
this requires either Fe or Co as the major constituent. 
2. In order to obtain a high coercive force, the material must consist of 
an assembly of small particles or crystallites. 
3. These particles or crystallites must exhibit microscopic magnetic 
anisotropy, i.e. they must have a preferred "easy axis" of magnetization. 
This can follow either from shape anisotropy or magneto-crystalline 
interaction. 
4. These microscopically anisotropic particles must be aligned 
substantially in parallel within the macroscopic assembly, in order to 
achieve values of Mr that approach Ms, i.e. square-loop behavior. 
The prior art teaches that good permanent magnetic materials, e.g., having 
maximum magnetic energy products of about 15 megagaussoersteds, consist of 
a conglomeration of non-interacting substantially crystallographically 
oriented uniaxial particles. When a sufficiently large magnetic field is 
applied in a given direction, the individual vector magnetizations of each 
of these particles point along the applied field, corresponding to the 
maximum or saturation value of the net magnetization, M.sub.s. As the 
applied magnetic field is reduced to zero, the vector magnetization of 
each particle relaxes back to the easy magnetic axis of the particle, so 
that the net resultant remanent magnetization, M.sub.r, may be less than 
M.sub.s. 
This is more fully elucidated by the following geometrical model, in which 
the "easy axis" of magnetization lies along a preferred axis, c. For an 
isolated uniformly magnetized particle, the magnetization vector, M, lies 
along the c axis for a zero applied field. If a field is applied in an 
arbitrary direction z, the magnetization is rotated away from the c axis 
until, at sufficiently large fields, M is parallel to z and M.sub.z is 
equal to M.sub.s. When the field is removed, the magnetization relaxes 
back parallel to the c axis, subject to the condition that the projection 
of magnetization along the c axis is positive. 
E. C. Stoner and E. V. Wohlfarth, Phil. Trans. Royal Soc. (London), A. 240, 
599 (1948) have calculated the hysteresis loop for such a particle for 
different orientations of the c axis with respect to z. For the case of a 
sample comprising a large number of such non-interacting particles 
oriented along some direction, the magnetic properties for the material or 
sample are the sum or average of the properties of the individual 
particles. Such a sample or material is hereinafter referred to as an 
anisotropic material. Anisotropic materials have at least one magnetic 
property which is a strong function of the direction of measurement. Such 
materials are characterized by a single "easy direction" of magnetization, 
where the value of the property greatly exceeds the value in other 
directions of magnetization. If the particles are non-interacting, the 
maximum energy product varies from a maximum value of 0.25 
(M.sub.s).sup.2, when z is parallel to the c axis, to 0 when z is 
perpendicular to the c axis. For a theoretical anisotropic material with 
M.sub.s equal to 16 and H.sub.c chosen to be greater than M.sub.s, the 
maximum theoretical value of the energy product of the hysteresis loop is 
64 megagaussoersteds. 
Stoner and Wohlfarth have carried out the same method of analysis for an 
ideal array of randomly oriented non-interacting uniformly magnetized 
particles. Since the array is isotropic there is no dependence of the 
hysteresis loop on the direction of the applied field. The maximum 
theoretical value of the energy product of such a loop is dependent on 
M.sub.s and H.sub.c. If M.sub.s is chosen to equal 16 kilogauss and 
H.sub.c is chosen to be much greater than M.sub.s, then the maximum energy 
product is 16 megagaussoersteds. 
Hence, the teaching of the prior art for a perfectly oriented 
non-interacting material (anisotropic) is that the maximum energy product 
is at least four (4) times that of the same material when randomly 
oriented (isotropic). 
For a general distribution of orientations of non-interacting particles, as 
a consequence of simple vector geometry, 
EQU (M.sub.r /M.sub.s)=[cos(theta)], 
where theta is the angle between the applied field and the easy axis of a 
given particle, and the result, indicated by double brackets, represents 
the size weighted average over all of the particles. As is well understood 
in the art, M.sub.r /M.sub.s =1 along the direction of orientation of a 
perfectly oriented, non-interacting, permanent magnet sample 
(anisotropic), and M.sub.r /M.sub.s =0.5 in all directions for a 
completely unoriented, non-interacting sample (isotropic). See, e.g., R. 
A. McCurrie, "Determination of the Easy Axis Alignment in Uniaxial 
Permanent Magnets for Remanence Measurements", J. Appl. Phys., Vol. 52, 
(No. 12), pages 7344-7346 (December 1981). Observations in the literature 
are consistent with this prediction. See, e.g., J. F. Herbst and J. C. 
Tracy, "On Estimating Remanent Magnetization from X-Ray Pole Figure Date", 
J. Appl. Phys., Vol. 50 (No. 6), pp. 4283-4284 (June 1979). 
A figure of merit, which applicants refer to as the magnetic retention 
parameter, is 
EQU Q=Sum.sub.x,y,z (M.sub.r M.sub.s).sup.2, 
where M.sub.s and M.sub.r are measured with the applied magnetic field 
along three orthogonal directions. Theoretically, for magnetic materials 
of the prior art, Q approaches 1 for perfectly oriented, non-interacting, 
particles or crystallites (anisotropic) and 0.75 for completely 
unoriented, non-interacting, crystallites (isotropic). The behavior for 
reported values of permanent magnetic materials of the prior art tend to 
produce values of Q which are substantially below the theoretical values. 
See, e.g., McCurrie; Herbst and Tracy; and Stoner and Wohlfarth; above. 
Prior art systems which are non-interacting and conform to the assumptions 
of and models in Stoner and Wohlfarth are described in the Background 
sections of commonly assigned copending U.S. application Ser. No. 816,778, 
filed Jan. 10, 1986, of R. Bergeron, R. McCallum, K. Canavan, and J. Keem 
for Enhanced Remanence Permanent Magnetic Alloy Bodies and Methods of 
Preparing Same, and U.S. application Ser. No. 893,516, filed Aug. 5, 1986 
of R. Bergeron, R. McCallum, K. Canavan, J. Keem, A. Kadin, and G. 
Clemente, for Enhanced Remanence Permanent Magnetic Alloy and Bodies 
Thereof. The prior art materials described and discussed in the Background 
sections of our earlier applications do not exhibit any deviations from 
the assumptions and models of Stoner and Wohlfarth. 
Deviations from (M.sub.r M.sub.s ) =[Cos(theta)]corresponding to larger 
values of Mr might be expected to occur if the particles were permitted to 
interact with one another. Suggestions of this sort have appeared in the 
magnetic recording literature, where the proposed interaction was due to 
long range magnetic dipole fields. See, for example, H. N. Bertram and A. 
K. Bhatia, The Effect of Interaction on the Saturation Remanence of 
Particulate Assemblies, IEEE Trans. on Magnetics, MAG-9, pp 127-133 
(1983), and R. F. Soohoo, Influence of Particle Interaction on Coercivity 
and Squareness of Thin Film Recording Media, J. Appl. Phys., Vol 52(3), pp 
2459-2461 (1981). However, this assumption of interactions has been 
questioned. See, for example, P. M. Davis, Effects of Interaction Fields 
on the Hysteretic Properties of Assemblies of Randomly Oriented Magnetic 
or Electric Moments, J. Appl. Phys., Vol 51 (2), pp 594-600 (1980). 
Suggestions of short range interactions based on exchange have also been 
made with respect to amorphous iron-rare earth alloys at cryogenic 
temperatures by E. Callen, Y. L. Liu, and J. R. Cullen, Initial 
Magnetization, Remanence, and Coercivity of the Random Anisotropy 
Amorphous Ferromagnet Phys. Rev. B, Vol. 16, pp 263-270 (1977). 
The literature does not contain any verified indications of enhanced values 
of Mr relative to those predicted by Stoner and Wohlfarth, above, in 
isotropic permanent magnetic materials. 
However, contrary to the limited but negative teachings of the prior art 
interaction between crystallites has been used to achieve enhanced 
magnetic properties in bulk solid materials. Magnetic materials which 
utilize interaction are described in commonly assigned copending U.S. 
application Ser. No. 816,778, filed Jan. 10, 1986, of R. Bergeron, R. 
McCallum, K. Canavan, and J. Keem for Enhanced Remanence Permanent 
Magnetic Alloy Bodies and Methods of Preparing Same, and U.S. application 
Ser. No. 893,516, filed Aug. 5, 1986 of R. Bergeron, R. McCallum, K. 
Canavan, J. Keem, A. Kadin, and G. Clemente, for Enhanced Remanence 
Permanent Magnetic Alloy and Bodies Thereof, both of which are 
incorporated herein by reference. 
Described therein is a class of permanent magnetic alloys which exhibit 
superior magnetic properties as measured in all spatial directions, that 
is, isotropically. The magnetic parameters are of a magnitude which the 
prior art teaches to be only attainable in one spatial direction, that is, 
anisotropically, and to be only attainable with aligned materials. 
The magnetic materials described in the incorporated patent applications 
have a ratio of net remanent magnetization (M.sub.r) to net saturation 
magnetization (M.sub.s), exceeding 0.5 and approaching 1.0, in all 
directions, without any significant preferred crystallite orientation. 
This is a clea violation of the consequences of the Stoner and Wohlfarth's 
model and the assumptions of the prior art that the grains must be 
microscopically anisotropic grains that are aligned substantially in 
parallel within the macroscopic body in order to achieve values of Mr 
approaching Ms, i.e., square hysteresis loop behavior. 
These permanent magnetic materials have isotropic magnetic retention 
parameters, Q, as described above, greater than 0.75 and preferably 
greater than 1. The theoretical limit of the magnetic retention parameter, 
Q, for the herein contemplated materials is believed to approach 3, rather 
than the theoretical values of 1.0 and 0.75 respectively, for aligned 
(anisotropic) and unaligned (isotropic), non-interacting materials of the 
prior art. 
Ribbon samples of the as quenched materials described above, without 
further processing, exhibit remanent magnetization, M.sub.r, greater than 
8 kilogauss, coercive force, H.sub.c, greater than 8 kilooersteds, and 
preferably greater than 11 kilooersteds, and maximum energy product 
(BH)max greater than 15 megagaussoersteds with similar values measured in 
all directions, i.e., in the plane of the ribbon and perpendicular to the 
plane of the ribbon. In the latter case the value was obtained after a 
standard correction (a geometric demagnetization factor as described, for 
example, in R. M. Bozorth, Ferromagnetism, D. VanNostrand Co., New York, 
(1951), at pages 845-847) for the shape anisotropy of the ribbon. 
The saturation magnetization M.sub.s of the ribbon, i.e., the magnetization 
in the limit for large applied fields, e.g., an applied magnetic field 
above about 50 kilogauss, is 15 to 16 kilogauss, also in all directions. 
In order to directly measure saturation magnetization, M.sub.s, the 
applied field should be at least three times the coercive force, H.sub.c. 
Alternatively, the value of M.sub.s can be estimated based on the values 
thereof for compositionally similar materials. The values correspond to a 
value of M.sub.r /M.sub.s greater than 0.5, and a magnetic retention 
parameter, Q, greater than 0.75, in contradistinction to the clear 
teachings of the prior art for a macroscopically isotropic, 
non-interacting material. 
Typical magnetic parameters for the magnetic alloys described in the above 
incorporated patent application are as shown in Table I of U.S. 
application Ser. No. 893,516, filed Aug. 5, 1986, Table V of U.S. patent 
application Ser. No. 816,778. (An M.sub.s of 16 kilogauss was used.) 
As can be seen from Table I of U.S. application Ser. No. 893,516, filed 
Aug. 5, 1986, the samples of the materials described therein exhibit 
superior relevant magnetic parameters throughout the volume of the bulk 
solid, evidencing interaction between grains. The properties are 
especially superior when compared with the properties of the isotropic 
materials of the prior art listed in Table III of U.S. application Ser. 
No. 816,778. When compared with the anisotropic prior art materials listed 
in Table IV of U.S. application Ser. No. 816,778, the samples of the 
inventions described in the aforementioned U.S. patent application Ser. 
Nos. 816,778 and 893,516 (filed Aug. 5, 1986) exhibit comparable but 
isotropic magnetic properties, and were prepared without the costly, 
complicated alignment steps necessary in the prior art. 
The magnetic alloy materials of U.S. application Ser. Nos. 816,778 and 
893,516 (filed Aug. 5, 1986) have been prepared by the melt spinning 
process, and more particularly by the free jet casting process. 
In the free jet casting process a jet of molten metal is expelled under a 
head of inert gas from a crucible onto a rapidly rotating chill wheel. 
This jet of molten metal forms a puddle of molten metal on a rapidly 
rotating chill wheel. The top of the puddle appears to stand stationary 
beneath the orifice of the crucible, while the bottom of the puddle 
appears to be continuously drawn away from the crucible orifice. We have 
observed an instability associated with the interaction between the chill 
wheel and the puddle. This instability is associated with a high degree of 
variance of magnetic properties of the cast products and a concommitant 
low yield of enhanced remanence magnetic alloy material. 
SUMMARY OF THE INVENTION 
These instabilities of the free jet casting process and the associated low 
yields of enhanced remanence magnetic material are obviated by the method 
of this invention. 
The magnetic material is prepared by a two step solidification, heat 
treatment process. The solidification process yields a very low coercivity 
material, characterized as being one or more of amorphous, 
microcrystalline, or polycrystalline. The grains within the solid have, at 
this stage of the process, an average grain characteristic dimension less 
than that of the heat treated magnetic material, and too small to provide 
a practical coercivity or an enhanced remanence. 
The solidification process is carried out by forming a solution of 
reducible precursor compounds of the magnetic material in a suitable 
solvent. A suitable reductant or reducing agent is used to reduce the 
reducible, precursor compounds and form a precipitate thereof. Typically 
the solvent is an aprotic organic solvent and the reducing agent is a 
strong reductant, e.g., lithium aluminum hydride. 
In the second, or heat treating, stage of the process, the atomized solid 
particles are heat treated to form a solid material having a morphology 
that provides a practical coercivity and the above described enhancement 
of remanence. The heat treated solid is comprised of grains meeting at 
grain boundaries, with the substantial absence of intergranular phases of 
different stoichiometry or structure. The grains and grain boundaries have 
the morphology of the enhanced remanence magnetic material.

DETAILED DESCRIPTION OF THE INVENTION 
According to the invention there is provided a method of forming a class of 
magnetic alloy materials having superior magnetic properties. These 
magnetic alloy materials are high remanence materials that do not obey the 
Stoner and Wohlfarth assumptions of non-interacting particles. To the 
contrary, the individual grains or crystallites interact across grain 
boundaries. The enhanced magnetic properties give clear evidence of this 
interaction across grain boundaries of the grian or crystallites. 
The alloy is a substantially crystallographically unoriented, substantially 
magnetically isotropic alloy, with interaction between adjacent 
crystallites. By substantially isotropic is meant a material having 
properties that are similar in all directions. Quantitatively, 
substantially isotropic materials include those materials where the 
remanence along all three orthogonal axis, after application of the 
appropriate geometric demagnetization factor, are interactively enhanced, 
i.e., greater than 8 kilogauss, as well as those materials where the 
average value of [Cos(theta)], defined above, is less than about 0.75 in 
all directions, where Cos (theta) is averaged over all the crystallites. 
Microscopically this means that the direction of the easy axis of 
magnetization is substantially random and substantially uncorrelated from 
grain to grain. 
The materials are permanent (hard) magnets, with isotropic magnetic 
parameters, i.e. isotropic maximum magnetic energy products greater than 
15 megagaussoersteds, magnetic retention parameters, Q, greater than 0.75, 
standard temperature coercivities greater than about 8 kilooersteds, and 
remanences greater than about 8 kilogauss, and preferably greater than 
above about 11 kilogauss. 
The saturation magnetization M.sub.s of the ribbon, i.e., the magnetization 
in the limit of large applied fields, is 15 to 16 kilogauss, also in all 
directions. These values correspond to a value of M.sub.r /M.sub.s greater 
than 0.5, and a magnetic retention parameter, Q, greater than 0.75, in 
contradistinction to the clear teachings of the prior art for a 
macroscopically isotropic material. 
The magnetic material is composed of an assembly of small crystalline 
ferromagnetic grains. 
The grains are in intimate structural and metallic contact along their 
surfaces, i.e., along their grain boundaries. They are characterized by 
the substantial absence of intergranular material of different 
stoichiometry or morphology. That is, one grain of the material is in 
direct contact with an adjacent grain of the material at a grain boundary 
that is substantially free of intergranular materials and/or phases. This 
is contradistinction of the clear teachings of Raja K. Mishra, 
"Microstructure of Melt-Spun Nd-Fe-B Magnequench Magnets," Journal of 
Magnetism and Magnetic Materials, Vol 54-57 (1986), pages 450-456 who 
teaches the necessity of a 10-20 Angstrom thick film of Nd-rich, B-lean 
phase, between Nd.sub.2 Fe.sub.14 B.sub.1 grains. Mishra reports that this 
film is necessary as a pinning site for magnetic domain walls. By way of 
contrast, according to the instant invention grains of magneticmaterial 
are in direct contact with adjacent grains of magentic material, e.g., 
grains o Nd.sub.2 Fe.sub.14 B. 
The degree of magnetic enhancement is determined by the average 
characteristic dimension of the grains, Ro, the size distribution of the 
individual grain dimensions relative to this characteristic scale, and a 
characteristic dimension of the grain boundaries. The characteristic 
dimension of the grain boundaries must be small enough to allow 
interaction between adjacent grains across the grain boundaries. 
The magnetic alloys are solidified or quenched to produce a precursor 
microstructure, which, when appropriately heat treated, results in a 
structure having these dimensions and morphologies and therefore 
exhibiting the above described improved magnetic parameters. These 
initially solidified particles much larger then the characteristic grain 
dimension R.sub.o. A particle may contain at least 10.sup.8 grains of 
characteristic grain size R.sub.o. 
The as heat treated dimensions and morphologies are critical in obtaining 
the enhanced remanence and magnetic retention parameters herein 
contemplated. 
While the illustrations of the interaction across grain boundaries in Ser. 
No. 893,516 have been quantitatively described with respect to rare 
earth-transition metal-boron materials of tetragonal, P4.sub.2 /mnm 
crystallography, especially the Nd.sub.2 Fe.sub.14 B.sub.1 type materials, 
this is a general phenomenon applicable to other systems as well. The 
optimum characteristic grain dimension R.sub.o, however, may be different 
in these other cases. 
We expect that for Pr.sub.2-x Nd.sub.x Fe.sub.14 B.sub.1, R.sub.o will be 
approximately 200 Angstroms for all values of x. For SmCo.sub.5, for 
example, where Curie temperature, Tc=900K, saturation magnetization, Ms=12 
kG, and Hanisotropy=300 kOe, H(spin,spin)=9 MOe, so that R.sub.o =(9 
MOe)/(300 kOe).times.2.5 Angstroms=(approximately) 80 Angstroms. 
Similarly, for Sm.sub.2 Co.sub.17 R.sub.o =(12 MOe)/(8 OkOe)2.5 
Angstroms=(approximately) 400 Angstroms. 
For randomly-oriented crystallites at the optimum size, the expected 
magnetic enhancement attributable to quantum mechanical magnetic coupling 
is comparable to that estimated above for Nd.sub.2 Fe.sub.14 B type 
material--an increase in BH.sub.max by a factor of 2 to 3 above that 
predicted by the Stoner and Wohlfarth model, above. 
The magnetic material is prepared by a two step precipitation, heat 
treatment process. The precipitation process yields a very low coercivity 
material, characterized as being one or more of amorphous, 
microcrystalline, or polycrystalline. The crystallites within the solid 
have, at this stage of the process, an average grain characteristic 
dimension less than that of the heat treated magnetic material, and too 
small to provide a practical coercivity. 
The solidification process is carried out by forming a solution of 
reducible precursor compounds of the magnetic material in a suitable 
solvent. A suitable reductant or reducing agent is used to reduce the 
reducible, precursor compounds and form a precipitate thereof. 
According to one embodiment of the invention reducible compounds of the 
elements of the magnetic alloy are introduced into a non-aqueous solvent, 
for example an aprotic solvent, and reduced with a strong reducing agent. 
The strong reducing agent is necessitated by the electronegativity of the 
rare earth metal. The strong reducing agents decompose water, 
necessitating an aprotic solvent. 
By a strong reducing agent is meant a reducing agent more electronegative 
then the rare earth component of the alloy. For example, neodymium has an 
ionization potential 
EQU Nd=Nd.sup.+3 +3e.sup.-, E=-2.246 V, 
of 2.246 volts. Suitable reducing agents include, for example, LiAlH.sub.4, 
or a dispersed (colliodal) alkali metal as Li, Na, K, Rh, or Cs (and 
especially Li, Na, and K). 
These strong reducing agents readily decompose water, yielding gaseous 
hydrogen. Thus, it is necessary to carry out the reduction in an aprotic 
solvent. Aprotic solvents are those solvents, typically hydrocarbons and 
derivatives thereof. Aprotic solvents have minimal tendency to either gain 
or lose protons. They are essentially inert, exhibiting essentially no 
levelling effect. Aprotic solvents are further characterized by low 
dielectric constants, e.g., less than 6, and generally from 2 to 6. 
Exemplary aprotic solvents include ethers, dimethyl sulfoxide (DMSO), 
dimethyl formamide (DMF), tetrahydrofuran (THF), trimethylamine (TMA), 
triethylamine (TEA). trialkylamines, and the like. 
According to a preferred exemplification which may have the flow chart 
shown in FIG. 1, simple salts of the rare earth metal, the iron, and boron 
are introduced into an aprotic organic solvent, and the solvent is reduced 
with a strong reducing agent. For example, simple halides, e.g., 
chlorides, bromides, iodides of (1) one or more of neodymium and 
praseodymium, and (2) iron, optionally with cobalt, are solublized with a 
simple borohydride, in an aprotic organic solvent. 
The salts are reduced to metal with a strong reductant, as lithium aluminum 
hydride, or a dispersed (colloidal) alkali metal. Reduction may be carried 
out in a quiescent solution, or it may be carried out in a continuously 
mixed solution, as a continuously totally refluxed solution. 
The metals may be precipitated directly upon reduction, thermally, by 
solvent extraction, change in pH, or further reaction. The precipitate may 
then be recovered by physical separation, as filtration, settling, 
sedimentation, centrifugation. Alternatively, the remaining lithium 
aluminum hydride, if any, may be neutralized, hydrolyzed, or decomposed, 
and the reduced materials thereafter precipitated, for example by the 
addition of a further solvent and/or a subsequent reaction or shift in the 
pH. 
In the second, or heat treating, stage of the process, the solid particles 
are heat treated to form a solid material having a morphology that 
provides a practical coercivity and the above described enhancement of 
remanence. The heat treated solid is comprised of grains meeting at grain 
boundaries. The grains and grain boundaries have the above described 
morphology associated with the enhanced remanence magnetic material. 
In one exemplification the magnetic alloy material is an alloy of iron, 
optionally with other transition metals, as cobalt, a rare earth metal or 
metals, boron, and a modifier. In another exemplification the magnetic 
alloy material is an alloy of a ferromagnetic transition metal as iron or 
cobalt, with an lanthanide, as samarium, and a modifier. 
A modifier is an alloying element or elements added to a magnetic material 
which serve to improve the isotropic magnetic properties of the resultant 
material, when compared with the unmodified material, by an appropriate 
processing technique. Exemplary modifiers are silicon, aluminum, and 
mixtures thereof. Alternative or additional modifiers may include lithium, 
hydrogen, fluorine, phosphorous, sulfur, germanium, and carbon. It is 
possible that the modifier acts as a grain refining agent, providing a 
suitable distribution of crystallite sizes and morphologies to enhance 
interactions. 
The amount of modifier is at a level, in combination with the quench 
parameters, to give the above described isotropic magnetic parameters. 
While the alloys referred to herein have modifiers, which are believed to 
control grain nucleation and growth, the crystallite size and size 
distribution may be obtained by proper choice and control of the 
solidification technique employed. For example, such solidification 
methods as gas atomization, metallization, chemical vapor deposition, and 
the like may be used as an alternative to rapid solidification from the 
melt even without the modifier. The modifier acts during solidification 
from the liquid state, or during grain nucleation and growth from the 
amorphous state, e.g., as a grain refining agent or a nucleating agent, to 
provide the distribution of crystallite size and morphology necessary for 
enhanced properties. 
When modifiers are indicated as being present, it is to be understood that 
other methods of providing nucleation sites and/or obtaining uniform grain 
size may be used. 
The magnetic alloy may be of the type [Rare Earth Metal(s)]-[Transition 
Metal(s)]-[Modifier(s)], 
for example 
[Sm]-[Fe, Co]-[Si, Al]. 
Another interacting alloy may be of the type [Rare Earth 
Metal(s)]-[Transition Metal(s)]-Boron-[modifier(s)], 
for example [Rare Earth Metal(s)]-[Fe,Co]-Boron-[modifier(s)], and [Rare 
Earth Metal(s)]-[Fe,Co,Mn]-Boron-[modifier(s)]. 
In one exemplification, the magnetic alloy material has the stoichiometry 
represented by: 
(Fe,Co,N).sub.a (Nd,Pr).sub.b B.sub.c (Al,Si).sub.d, exemplified Fe.sub.a 
(Nd,Pr).sub.b B.sub.c (Al, Si).sub.d, 
where a, b, c, and d represent the atomic percentages of the components 
iron, rare earth metal or metals, boron, and silicon, respectively, in the 
alloy, as determined by energy dispersive spectroscopy (EDS) and wave 
length dispersive spectroscopy (WDS) in a scanning electron microscope; 
a+b+c+d=100; 
a is from 75 to 85; 
b is from 10 to 20, and especially from 11 to 13.5; 
c is from 5 to 10; 
and d is an effective amount, when combined with the particular 
solidification or solidification and heat treatment technique to provide a 
distribution of crystallite size and morphology capable of interaction 
enhancement of magnetic parameters, e.g., from traces to 5.0. 
The rare earth metal is a lanthanide chosen from neodymium and 
praseodymium, optionally with other lanthanides (one or more La, Ce, Sm, 
Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), Sc, Y, and mixtures thereof 
present. While various combinations of the rare earth metals may be used 
without departing from the concept of this invention, especially preferred 
rare earth metals are those that exhibit one or more of the following 
characteristics: (1) the number of f-shell electrons is neither 0 (as La), 
7 (as Gd) or 14 (as Lu), (2) low molecular weight lanthanides, such as La, 
Ce, Pr, Nd, and Sm, (3) high magnetic moment lanthanides that couple 
ferromagnetically with iron, as Nd and Pr, or (4) relatively inexpensive 
lanthanides, as La, Ce, Pr, and Nd. Especially preferred are Nd and Pr. 
Various commercial and/or byproduct mischmetals may be used. Especially 
preferred mischmetals are those rich in Nd and/or Pr. 
While the invention has been described with respect to certain preferred 
exemplifications and embodiments thereof, it is not intended to limit the 
scope of the invention thereby, but solely by the claims appended hereto.