Abstract:
A new alloy for permanent magnets which is of the composition (R x  Fe y-w  Co w  M z )L.sub.α transition metals M such as, but not limited to Cr, Mo, Ti and V and mixtures thereof. R would be rare earth metals such as, but not limited to Nd, Pr, Dy and Tb, other rare earths, Y, and La and mixtures thereof. L is carbon or nitrogen or a mixture thereof. x+y+z equals 100 atomic %, x is from about 5 to about 20%, y is from about 65 to about 85%, z is from about 6 to about 20%, w≦20%, and α is from about 4 to about 15%. We have also developed a new process whereby the alloy metal magnets are formed by taking the ingredients and arc melting the individual elements R, Fe, Co and M at least once whereby forming an alloy ingot, and if necessary, remelting the alloy ingot as many times as necessary and reforming the alloy to form a more uniform alloy. The alloy formed is then ground into a powder. The powders are then formed into magnets and are bonded at high temperatures.

Description:
BACKGROUND OF THE INVENTION 
     It has been known in the art of permanent magnets to use mechanical alloying and apply it to prepare Nd 2  Fe 14  B 1  (2:14:1 Phase), Sm(Fe--TM) 12  (1:12 Phase) and interstitial nitrided and carbided permanent magnets wherein the transition metal (TM) is V, Ti and Zr. However, if Nd 2  Fe 17  (2:17) phase or Sm(FeTM) 12  is nitrogenated or carbonated the coercivity becomes very low. The prior art started from elemental powders, the hard magnetic phases are formed by milling followed by solid state reaction at relatively low temperatures. In Nd--Fe--B, the magnetic isotrope particles are microcrystalline, show a high coercivity (up to 16 kA/cm for ternary alloys and above for Dy-substituted samples) (J. Appl. Phys. No. 70 (10), Nov. 15 1991, pp. 6339-6344). In the prior art the previous 1:12 alloys were based on Sm-containing compounds. Sm, however, is an expensive rare earth metal as compared to Nd and Pr. We have discovered a new permanent magnet based on the 1:12 phase that does not require the use of the expensive Sm rare earth metal. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to fabricate a permanent magnet having very high coercivities while maintaining a high magnetic moment and Curie temperature T c . It is a further object of this invention to develop a process to manufacture a magnet having high coercivities while maintaining a high magnetic moment and high T c . We have discovered a new alloy for permanent magnets which is of the composition (R x  Fe.sub.(y-w) Co w  M z )L.sub.α wherein x+y+z equals 100 in atomic percent; w is from zero to about 20%; x is from about 5 to about 20%; y is from about 65 to about 85% and z is from about 6 to about 20%. M would be transition metals, preferably W, Mn, Cr, Mo, Ti and V and mixtures thereof. R would be rare earth metals, preferably Nd, Pr, Dy, Tb and Mm (mish-metal rare earth) and mixtures thereof. L would be carbon or nitrogen or mixture thereof. α would be from about 4 to about 15 %. We have also developed a new process whereby the alloy metal magnets are formed by taking the ingredients and are melting the individual elements R, Fe, Co and M at least once whereby forming an alloy ingot, and if necessary, remelting the alloy ingot as many times as necessary and reforming the alloy to form a more uniform alloy. The alloy formed is then ground into a powder. The powders are then formed into magnets and are bonded at high temperatures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows three hysteresis loops of Nd 10  Fe 75  Mo 15 , Nd 10  Fe 75  Mo 15  N x  and Nd 10  Fe 75  Mo 15  N x  +Al; 
     FIG. 2 shows the coercivity of magnets as a function of Al content (0-40%) at different bonding temperatures; 
     FIG. 3 shows the coercivity of Nd 10  Fe 75  Mo 15  N x  and Nd 10  Fe 75  Mo 15  C x  samples as a function of nitrogenation or carbonation for 2 hours and 
     FIG. 4 shows the temperature dependence of H c  for Nd 10  Fe 75  Mo 15 , Nd 10  Fe 75  Mo 15  N x  and Nd 10  Fe 75  Mo 15  C x  compounds. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The object of this invention is to make permanent magnets from (R x  Fe.sub.(y-w) Co w  M z )L.sub.α wherein M would be transition metals preferably W, Mn, Cr, Mo, Ti and V and mixtures thereof and R would be rare earth metals preferably Nd, Pr, Mm, Dy and Tb and mixtures thereof, in particular at least Nd or Pr or mixture thereof and optionally Mm, Dy and Tb. L is carbon or nitrogen or a mixture thereof. x+y+z being equivalent to 100 atomic %, &#34;w&#34; is from zero to about 20, preferably up to about 10%; &#34;x&#34; is from about 5 to about 20%, preferably about 8 to about 15%, and more preferably 10 to about 12%; &#34;y&#34; is from about 65 to about 85 %, preferably about 70 to about 80% and more preferably about 75 to about 80%; &#34;z&#34; is from about 6 to about 20%, preferably about 10 to about 20% and more preferably about 10 to about 16%, and &#34;α&#34; is from about 4 to about 15%. Generally Dy and Tb or mixtures of Dy and Tb would be in an amount up to about 10% at most. 
     Additions of cobalt, up to about 20% leads to further increase of the Curie temperature (T c ). The iron and cobalt gives most of the magnetic induction. The R provides the anisotropy. The M elements help to form a particular R--Fe--M phase, the 1:12 phase having a high magnetic moment and high T c . 
     The permanent magnets are made by the following process. First the elemental R, Fe and M are made into an alloy ingot by are melting in an inert gas, preferably argon. The are melting forms an alloy ingot. The alloy ingot can then be are melted in an inert gas several more times in order to form a more homogenous alloy. It should be are melted at least one time and preferably are melted three or four times. The are melting temperature must be greater than the highest melting point of all the elements. 
     The R--Fe--M alloys are milled in a high energy ball miller under inert gas, preferably using argon atmospheres resulting in a microstructure which is a mixture of a non-equilibrium phase with some amorphous phase. The high energy ball billing leads to a nano crystalline structure which is a mixture of α-Fe with some amorphous phase. The ball-milled powders are heat treated in the temperature range of about 500° to about 1000° C. and preferably about 700° to 850° C. for about 15 minutes to about 60 minutes where a nano-crystalline 1:12 structure is formed. The hard magnetic properties of the R--Fe--M powders are obtained after nitrogenation or carbonation at temperatures in the range from about 400° to about 700° C. for about 1 to about 4 hours using about a 50 kPa pressure of nitrogen or methane (CH 4 ). The R--(FeM) 12  compounds are drastically changed after nitrogenation resulting in increases in the Curie temperature T c  saturation magnetization M s  and anisotropy constant K, which make these compounds candidates for permanent magnet. The R--Fe--M magnets were metal bonded at temperatures from about 400° to about 700° C. preferably about 400° to about 600° C. using fine powders of low melting point materials such as, but not limited to, zinc or aluminum with a size of about 20 μm. 
     The advantage of our process is that the magnets are made from alloy powders and not from elemental powders as is usually the case. The rare earth elements are very expensive. This process protects the rare earth elements from oxidation. Therefore, less rare earth elements are needed. Usually, in the prior art, the rare earth powders are easily oxidized in the fine particle form and that is one of the advantages to using an alloy powder mix to prevent this oxidation. In addition, a small excess of R in the R--Fe--M system leads to a high coercivity in the nitrogenated powder which has a single phase (ThMn 12  -type). Another advantage is the R--Fe--Mo--N x  is quite stable at high temperatures (about 650° C.). The R--Fe--Mo--N x  can be bonded with aluminum powders at high temperatures. The R--Fe--Mo--N x  and R--Fe--Cr--N x  magnets are a new kind of permanent magnets which have a high magnetization, anisotropy, and a high Curie temperature and, therefore a great potential for permanent magnet development. 
     Nd 2  Fe 14  B 1  has a T c  of about 310° C. while we have been able to achieve a much higher Tc according to the invention. 
     Listed below are some of the examples of magnetic properties of Nd--Fe--Cr nitrides (Tables 1-5). 
     Experimental Results of Nd--Fe--Cr Nitrides are as follows: 
     The coercivities of the Nd 10  Fe 75  Cr 15  N x  compounds were found to depend on the preparation conditions especially on the crystallization temperature T Cry  and nitrogenation temperature T N  as summarized in Table 4. The highest coercivity obtained was 4.5 kOe at T cry  equivalent to 800° C. for 30 minutes and T N  equivalent to 580° C. for 2 hours. The magnetization M s  at 55 kOe of the compounds was 105 and 101 emu/g at 273K and 10K, respectively. The magnetization M s  was lower at 10K because the maximum magnetic fields was not high enough to saturate the magnetization. The x-ray diffraction peaks of the nitrogenated sample were shifted to lower angles. The interstitial nitrogen atoms lead to an increase of saturation magnetization, Curie temperature and magnetic anisotropy. 
     When the chromium content is reduced from 15 to 12 at %, the coercivities of Nd 10  Fe 78  Cr 12  N x  compounds were decreased (Table 5). The highest H c  =3.4 kOe was obtained in sample prepared at T cry  being equivalent to 800° C. for 30 minutes and T N  being equivalent to 520° C. for 2 hours. The magnetization curves of the Nd 10  Fe 78  Cr 12  N x  sample have M s  equivalent to 127 emu/g and H c  equivalent to 3.0 kOe at 273K and M s  equivalent to 130 emu/g and Hc=12 kOe at 10K. Compared to the Nd 10  Fe 75  Cr 15  N x  compound, the decrease in coercivity was about ΔHc=1.5 kOe. 
     When the neodymium content increased from 10 to 12 at %, the coercivities of Nd 12  Fe 73  Cr 15  N x  compounds increased in as shown in Table 1. The best coercivity H c  was equivalent to 6.5 kOe was obtained after T Cry  at 700° C. for 30 minutes and T N  at 520° C. for 2 hours (see Table 2). The increase in coercivity was about ΔH c  equivalent to 2.0 kOe when the Nd content increased by 2 at % in the Nd 12  Fe 73  Cr 15  N x  compounds. 
     Nd 12  Fe 73  Cr 15  N x  nitrides were bonded at temperatures in the range of 480°-520° C. for 1 hours using AgCl and CuBr powders. Unfortunately, the coercivities of the bonded magnets were reduced quickly to 0.5 kOe when the bonding temperature increased to 520° C. (see Table IV). It may be AgCl and CuBr powders have a chemical reaction with the 1:12 phase and destroy the hard magnetic phase. An increased α-Fe precipitation (out of the 1:12 phase) was observed in the bonded samples by x-ray diffraction. 
     
                       TABLE 1______________________________________Magnetic Properties of Nd--fe--Cr Nitrides      Ms         Hc      Tc      (emu/g)    (kOe)   (°C.)______________________________________Nd.sub.10 Fe.sub.78 Cr.sub.12 N.sub.x        133          3.0     478Nd.sub.10 Fe.sub.75 Cr.sub.15 N.sub.x        112          4.5     480Nd.sub.12 Fe.sub.73 Cr.sub.15 N.sub.x        105          6.5     460______________________________________ Ms = Saturation magnetization Hc = Coercivity Tc = Curie temperature 
    
     
                       TABLE 2______________________________________Magnetic properties of Nd.sub.12 Fe.sub.73 Cr.sub.15 nitrides afterdifferent crys-talization temperatures T.sub.cry and nitrogenation temperaturesT.sub.N.T.sub.cry      T.sub.N(°C.)   (°C.)                 H.sub.c (kOe)______________________________________650            520    6.3700            520    6.5750            520    5.5650            550    5.1700            550    6.3750            550    5.2800            550    4.1850            550    4.3700            580    4.4750            580    4.3800            580    4.2850            580    4.6700            610    2.2750            610    2.2800            610    2.6850            610    3.0______________________________________ 
    
     
                       TABLE 3______________________________________Nd.sub.12 Fe.sub.73 Cr.sub.15 nitrides bonded byCuBr and AgCl powders at different temperatures T.sub.bondT.sub.bond    H.sub.c (kOe)                  H.sub.c (kOe)(°C.)  CuBr     AgCl______________________________________480           2.0      3.0500           1.0      3.0520           0.3      0.5______________________________________ 
    
     
                       TABLE 4______________________________________Coercivities of Nd.sub.10 Fe.sub.75 Cr.sub.15 N.sub.x at differentpreparation conditions.T.sub.cry (°C./30 min)           T.sub.N (°C./2 hr)                      H.sub.c (kOe)______________________________________850              0         0.2800             530        1.1850             530        1.2900             530        1.6800             580        4.5850             580        3.5900             580        3.2750             590        1.5800             590        3.9850             590        3.6900             590        2.8750             620        0.5800             620        1.6850             620        2.5900             620        2.4______________________________________ 
    
     
                       TABLE 5______________________________________Coercivities of Nd.sub.10 Fe.sub.78 CrN.sub.x at different preparationconditions.T.sub.cry (°C./30 min)           T.sub.N (°C./2 hr)                      H.sub.c (kOe)______________________________________800             520        3.4850             520        3.2900             520        2.1______________________________________ 
    
     The advantages of Nd--Fe--M (M=Ti, V, Mo) are described in an article we wrote, which was published September, 1992 in IEEE Transactions on Magnetics, Vol. 28, No. 5, which is incorporated by reference, entitled &#34;Nitrogenated 1:12 Compounds by Mechanical Alloying&#34;. 
     Detailed lattice parameters are summarized in Table 6, for Nd 10  Fe 90-y  M y  (M=Ti, y=8), Mo and V; y=8, 15). The change in unit cell volume upon nitrogenation was ΔV/V=5.5, 3.0 and 3.6% for M=Ti, Mo and V. It is found that ΔV/V of mechanically alloyed powders is larger than that of as-cast alloy powders. It appears that nitrogen enters the ThMn 12  structure more easily in powders with smaller grains at lower nitrogenation temperatures. 
     The interstitial nitrogen atoms lead to an increase of saturation magnetization M s , Curie temperature T c  and anisotropy constant K. The magnetic properties of all samples were summarized in Table 7. The saturation magnetization was found using the law of approach to saturation by plotting M as a function of 1/H 2  and extrapolating to infinite fields. The changes in Curie temperature upon nitrogenation were almost the same, about 30%, for the three compounds listed in Table 7. The increase of Curie temperature is caused by an enhancement of Fe--Fe exchange interactions due to the increase in lattice parameters. The coercivity H c  is increased from 0.5 to 7.5 kOe after nitrogenation. 
     
                       TABLE 6______________________________________Lattic parameters ofmechanical alloyed Nd (FeM).sub.12 upon nitrogenation.       a (Å)            c (Å)                     V (Å.sup.3)                             ΔV/V %______________________________________Nd.sub.10 Fe.sub.82 Ti.sub.8         8.598  4.779    353.29Nd.sub.10 Fe.sub.82 Ti.sub.8 N.sub.x         8.756  4.861    372.67                               5.5Nd.sub.10 Fe.sub.75 Mo.sub.15         8.612  4.823    357.75Nd.sub.10 Fe.sub.75 Mo.sub.15 N.sub.x         8.692  4.876    368.39                               3.0Nd.sub.10 Fe.sub.75 V.sub.15         8.562  4.775    350.04Nd.sub.10 Fe.sub.75 V.sub.15 N.sub.x         8.646  4.851    362.64                               3.6______________________________________ 
    
     
                                           TABLE 7__________________________________________________________________________Magnetic properties ofmechanically alloyed Nd (FeM).sub.12 powders upon nitrogenation.    Tc ΔTc/Tc            Ms.sub.(10K)                 Hc.sub.(10K)                     Ms.sub.(295K)                          Hc.sub.(295K)    (K)       (%)  (emu/g)                 (kOe)                     (emu/g)                          (kOe)__________________________________________________________________________Nd.sub.10 Fe.sub.82 Ti.sub.8    551     129.8                 4.5 113.2                          0.5Nd.sub.10 Fe.sub.82 Ti.sub.8 N.sub.x    716       30   140.4                 7.0 132.6                          2.5Nd.sub.10 Fe.sub.75 Mo.sub.15    450     106.6                 3.0 72.8 0.5Nd.sub.10 Fe.sub.75 Mo.sub.15 N.sub.x    578       30   91.5 28.0                     85.0 8.0Nd.sub.10 Fe.sub.75 V.sub.15    583     103.2                 1.5 91.4 0.5Nd.sub.10 Fe.sub.75 V.sub.15 N.sub.x    768       32   119.5                 30.0                     131.0                          7.5__________________________________________________________________________ 
    
     The advantages of mechanically allowed 1:12 nitrides and carbides is described in an article entitled &#34;Mechanically Alloyed 1:12 Nitrides and Carbides&#34; which has been submitted by us to the publisher and will be published in the Journal of Applied Physics, Volume 73(10), May 15, 1993 and is enclosed and incorporated by reference. 
     X-ray diffraction measurements confirmed that the Nd 10  Fe 82  Mo 8  compound is still a single 1.12 phase with a tetrgonal structure like the Nd 10  Fe 75  Mo 15  compound. It is obvious that with decreasing Mo content, M s  and T c  increase. The increases were about ΔM s  =24 emu/g and ΔT c  being equal to 45° C. for Mo content being from 15 to 8%. However, the coercivity was reduced from 8 to 4.6 kOe. Also the lower Mo content samples were not stable at higher nitrogenation temperatures. α-Fe appears to precipitate out at 610° C. when Mo is at about 8 at. % as compared to 860° C. for the Mo sample at 15%. The experimental data are summarized on Table 8. 
     A careful experiment with weight analysis for Nd 10  Fe 75  Mo 15  N x  nitrides showed that higher value of H c , M s  and T c  were related to the higher nitrogen content obtained at the higher nitrogenation temperatures. All the experimental data are summarized in Table 9. The weight increase in weight percent of the sample upon nitrogenation is given by ΔW=(W N-  W)/W, where W and W N  are the weights of the sample before and after nitrogenation. A maximum N content with x being equal to 10% in the Nd 10  Fe 75  Mo 15  N x  sample was obtained after nitrogenation at 650° C. for 2 hours resulting in the best hard magnetic properties H c  =8.0 kOe, M x  =84.5 emu/g and T c  =310° C. The x value of N content in the mechanically alloyed samples is much higher than the reported value in as-cast alloys, x=0.5 at. % in NdFe 10  Mo 2  N x . When the nitrogenation temperature is higher than 700° C., the weight analysis still shows an increase in the x value but the coercivity of the sample is lower because α-Fe is precipitated out of the 1:12 phase. 
     
                       TABLE 8______________________________________Magnetic properties of Nd.sub.10 Fe.sub.(90-y) Mo.sub.y N.sub.x samplesY         Ms       Hc.sub.(R.T.)                         Hc.sub.(10K)                               Tc(at %)    (emu/g)  (kOe)      (kOe) (°C.)______________________________________ 8        108.5    4.0        19    35512        99.0     6.0        21    33515        84.5     8.0        29    310______________________________________ 
    
     
                       TABLE 9______________________________________Room temperature magnetic properties M.sub.s, H.sub.cand T.sub.c of Nd.sub.10 Fe.sub.75 Mo.sub.15 N.sub.x (N.sub.x, x = 5-15)compound as a func-tion of nitrogen content x at different nitrogenation temperatures.T.sub.N ΔW           x       M.sub.s                          H.sub.c                                T.sub.c(°C./2 hr)   (wt %)  (at %)  (emu/g)                          (kOe) (°C.)______________________________________ 0      0        0      73.5   0.5   177550     1.44     7      79.5   3.5   230600     1.74     8      82.0   5.2   260650     2.02    10      84.5   8.0   310700     2.59    13      76.5   4.0     310, 770______________________________________ 
    
     Listed below are only some of the examples of Nd--Fe--Mo--Nx samples on different prepared conditions (crystallization temperature T cry  and nitrogenation temperature T nitro  ) in Tables 10-12. 
     
                       TABLE 10______________________________________Dependence of Coercivity on the BondingTemperature in Nitrogenated Nd.sub.10 Fe.sub.78 Mo.sub.12 (with VSM):T.sub.cry (°C.)         T.sub.nitro (°C.)                   Hc (kOe)______________________________________800           630       5.8850           630       5.8900           630       5.5______________________________________ 
    
     
                       TABLE 11______________________________________Magnetic properties of Nitrogenated Nd.sub.10 Fe.sub.82 Mo.sub.8T.sub.cry (°C.)         T.sub.nitro (°C.)                   Hc (kOe)______________________________________700           500       0.9750           500       1.8800           500       2.8850           500       2.9900           500       2.3700           550       0.9750           550       3.1800           550       4.5850           550       3.5900           550       3.2700           600       1.2750           600       2.9800           600       4.2850           600       4.3900           600       4.7700           650       0.6750           650       0.7800           650       1.2850           650       1.8900           650       1.6______________________________________ 
    
     
                       TABLE 12______________________________________Dependence of coercivity oncrystallization temperature Tcry and Nitrogenatedtemperature Tnitro for Nd.sub.10 Fe.sub.75 Mo.sub.15 Nx samples andT.sub.cry (°C.)         T.sub.nitro (°C.)                   H.sub.c (kOe)______________________________________700           600       3.8750           600       4.8800           600       7.5850           600       8.0700           630       5.0750           630       4.3800           630       7.2850           630       8.0850           570       7.6850           660       7.0850           680       6.0850           700       5.5______________________________________ 
    
     Al-bonded magnets were made with the Nd 10  Fe 75  Mo 15  N 10  powders which gave us the best results after nitrogenation. Three hysteresis loops of Nd 10  Fe 75  Mo 15 , Nd 10  Fe 75  Mo 15  N x  and Nd 10  Fe 75  Mo 15  N x  +Al are shown in FIG. 1. The coercivity of the magnets as a function of the amounts of Al powders (0-40 wt. %) at different bonding temperatures. An average increase of the coercivity by about ΔH c  =2.0 kOe was observed. The higher H c  obtained in the bonded magnets was 8.8 kOe (H c  =9.5 kOe in a saturation field 55 kOe) when the bonding temperature was close to the melting temperature of Al at 660° C. for 1 hour. The coercivity increases initially with Al content in the range of 0-5 wt. % and at bonding temperatures 640°-660° C. Higher Al contents did not affect the coercivity but they hardened the samples. Al was found to surround the grains in the Al-bonded magnets as observed by microscopy and EDAX. Below the Al melting point, the Al powders do not influence the surface of the grains in the mechanically alloyed powders. However, above the Al melting point, the Nd 10  Fe 75  Mo 15  N x  nitride is decomposed into two phases, 1:12 and α-Fe. Therefore, the coercivity of the magnets is low in both of the above cases (see FIG. 2). 
     A small amount of Dy was used to improve the hard magnetic properties. An increase in coercivity by 2-3 kOe was obtained in Nd 10  Fe 82  Mo 8  N x  after an addition of 1.5 at. % Dy in the Nd 8 .5 Dy 1 .5 Fe 82  Mo 8  N x  compound. The Nd 8 .5 Dy 0 .15 Fe 82  Mo 8  N x  nitride powders were bonded with Zn powders at temperatures 410°-440° C. The data show that the coercivity does not change in all the bonded magnets, made with a value around 6.6 kOe. One of reasons may be the absence of the Fe--Zn phase which was observed in Sm 2  Fe 17  N x  +Zn-bonded magnets. The magnetic properties of three typical samples are summarized in Table 13. 
     
                       TABLE 13______________________________________Magnetic properties of three typical Nd--Fe--Mo samples.Sample          M.sub.s (emu/g)                     H.sub.c (kOe)                              T.sub.c (°C.)______________________________________Nd.sub.10 Fe.sub.82 Mo.sub.8 N.sub.x           108.5     4.0      355Nd.sub.8.5 Dy.sub.1.5 Fe.sub.82 Mo.sub.8 N.sub.x           105.0     6.6      360Nd.sub.8.5 Dy.sub.1.5 Fe.sub.82 Mo.sub.8 N.sub.x + Zn            92.0     6.6      360(10 wt %)______________________________________ 
    
     Listed below are only some of the examples of temperature dependence of magnetic properties in Al bonded Nd 10  Fe 78  Mo 12  Nx and Nd 10  Fe 15  Mo 15  Nx below room temperature (see Tables 14-15). 
     
                       TABLE 14______________________________________Temperature Dependence of Coercivity Below RoomTemperature in A1 Bonded Nd.sub.10 Fe.sub.78 Mo.sub.12 (with SQUID):T (K) M.sub.55kOe (emu/g)             Ms (emu/g) Mr (emu/g)                                 Hc (kOe)______________________________________ 10   77.2        83.0       45.8     22 77   81.2        87.8       51.7     20150   86.2        93.5       54.4     15220   89.5        96.0       52.0     11273   91.0        99.0       47.8      7______________________________________ 
    
     
                       TABLE 15______________________________________Coercivity of A1 Bonded Samples at Low Temperaturesfor Nd.sub.10 Fe.sub.75 Mo.sub.15 nitrogenated magnet (measured withSQUID):T (K) M.sub.55kOe (emu/g)             Ms (emu/g) Mr (emu/g)                                 Hc (kOe)______________________________________10    51.9        60.0       24.9     2377    58.9        63.0       35.2     22273   66.0        72.5       35.0     9.5______________________________________ 
    
     Interstitial carbon atoms were found to increase the lattice constants of Nd 10  Fe 75  Mo 15  compounds. The hard magnetic properties Nd 10  Fe 75  Mo 15  C x  carbides with 1:12 phase are enhanced upon carbonation with M x  =78.7 emu/g and T c  =310° C., same as in Nd 10  Fe 75  Mo 15  N x  nitrides. However the coercivity of the 1:12 carbides was lower than the 1:12 nitrides. The coercivity of both the Nd 10  Fe 75  Mo 15  N x  and Nd 10  Fe 75  Mo 15  C x  samples as a function of nitrogenation and carbonation treatment temperature the high H c  of 1:12 carbides was 4.0 kOe after carbonation at 650° C. for 2 hours. It is clear that hard magnetic properties of 1:12 carbides are inferior to those of the 1:12 nitrides. 
     The coercivity of mechanically alloyed powders does not depend only on the magnetic structure induced by nitrogenation but also on the microstructure which strongly depends on the crystallization temperature. For best permanent magnetic properties of these samples a higher N content and grain size about 4000 Å were required. 
     The magnetic properties of Nd 10  Fe 75  Mo 15  N x  compound depend strongly on the N content. A maximum N content x-10 atomic % was obtained in the Nd 10  Fe 75  Mo 15  N x  sample with the best hard magnetic properties; H c  =8.0 kOe, M x  =84.5 emu/g, and T c  =310° C. 
     When the Mo content is reduced from 15 to 8 atomic % in Nd 10  Fe 90-y  Mo y  N x , the Nd 10  Fe 82  Mo 8  N x  the 1:12 single phase is maintained but with a lower H c  =4.0-4.5 kOe. An increase in coercivity by 2-3 kOe was obtained after the addition of 1.5 at. % Dy. No change in coercivity was observed in Zn-bonded magnets (Table 16). 
     The Nd 10  Fe 75  Mo 15  C x  carbide has the same behavior as Nd 10  Fe 75  Mo 15  N x , but with a much lower coercivity, H c  =4.0 kOe. The experimental data are summarized in FIG. 3. 
     At low temperature, both the nitrides and carbides appear to have very high coercivities, H c  &gt;22 kOe (FIG. 4). 
     As stated above, this invention can be practiced with carbides as well as nitrides. We have found a composition that will enable one to achieve high coercivities while being able to maintain high magnetic moments and Tc. Normally when one increases the magnetic moment it is at the expense of the coercivity. This also is true for increasing the coercivity at the expense of the moment. 
     
                       TABLE 16______________________________________Coercivities ofNd.sub.8.5 Dy.sub.1.5 Fe.sub.82 Mo.sub.8 N.sub.x as a function of Zncontent.Zn (wt %)      T.sub.bond (°C./hs)                     H.sub.c (kOe)______________________________________5              410        6.010             410        6.520             410        6.85              420        6.010             420        6.520             420        6.65              440        6.510             440        6.620             440        6.5______________________________________