IL31907A - Permanent magnetic materials - Google Patents

Description

MATERIALS WESTERN ELECTRIC MATERIALS Abstract of the The describee compositions of the ternary earth and related wherein the cobalt aay be partially or substituted with or Certain of the included have of teeny thousands of Nesbitt B ckground of the Invention of the Invention The invention concerned with magnet materials aone of which manifest exceedingly high coerelvltlea and to for their aaterials nay have large energy in are useful appliaationa aa torque loud so and the like which the magnetic usually an air Description of the Art As 38 Journal of Applied Page 1001 it has been known for that certain compounds of many of the lanthanide rare earth metal and related elements have permanent properties in powder These materials of such have high crystalline aniaotropy and high ooeroivitlea of 9000 oersteds and higher have been Measured on sufficiently to inhibit substantial domain motion of the order of 10 ad While as reported in the cited these are considered for fine particle permanent attempts to retain pensanent magnet properties in solid bodies have been of the Invention The invention la a series of permanent eagnet compositions and for their The inventive compositions in specific regions of the ternary eye represented by where A la or cobalt or a mixture B nickel or aluminum or mixtures of copper with aluminum or and the rare 2 1 holmium or the 2 rare earth related lanthanum and yttrium 3 tuted in their entirety or admixed in lesser For convenience all of the latter group of elements are referred 5 to as rare earth elements represented by the symbol 6 Certain of these compositions fall on the 7 stoichiometric line between the and In these 8 compounds the stoichiometric relationship of five trivalent cations 9 for each rare earth anion is preserved 0 this stoichiometric relationship does not follow the usual 1 ionic relationship and thus suggests the existence of 2 related compounds which do not possess a total of six Compositions which deviate from those having can be prepared and exhibit magnetic 5 properties comparable to those of the These compositions within the region bounded by the and and between 20 per cent and 100 per cent A and 2 per cent to 100 per cent The per cents given in this description refer in every case to atomic per each case it is the A iron that provides the magnetic Diluting the A component with element B decreases the saturation magnetization of the overall The component B is responsible for minimizing or eliminating domain wall motion so that increasing amounts result in increasing The dramatic improvements in coercivity thus obtained contributes one of the unobvious features Useful improvements in this 1 regard from the inclusion of component B in amounts of 2 greater than 1 7 atomic per cent and less than atomic 3 per These values correspond to the molar range of 4 2 per cent to 80 per cent of component B calculated as where x again is from about about 8 6 Although these compositions may be referred to as 7 intermetallic compounds it is perhaps more meaningful to allude 8 to the entire composition as a solid In so 9 it should be understood that the terminology is not intended to 10 indicate complete In based on the reported 11 powder work and on general understanding of other permanent 12 magnetic it is most probable that regions of the 13 compound are somehow separated by regions of the compound so as to reduce domain wall 15 The essence of the invention is the retention of 16 certain permanent magnet properties in comparatively massive While bodies show sufficient magnetic properties 18 for many a preferred aspect of the invention derives from the discovery that a low temperature anneal may further 20 enhance these Under certain circumstances still 21 further improvement may be achieved by preparing powders from 22 the cast materials and by carrying out a further series of 23 operations on these For they may be oriented within a magnetic and finally sintered or otherwise fixed in position so as to produce a new solid Since the 26 cast body shows the general effects of single domain particles 27 it is not necessary to produce powders of the fine sizes 28 required 29 Brief Description of the Drawing 30 1 is a ternary composition diagram for the system 1 where A is cobalt or iron or a mixture B is 2 nickel or aluminum or mixtures of copper with nickel or 3 from the group consisting of neodymium and holmium describing the compositions within the scope of the on coordinates of coercivity in oersteds and composition terms of the atomic ratio of B to A in the general formula is a graph showing the relationship between these two parameters for and also for subsequently annealed material for the compositional system along the RE RE 5 5 on coordinates of saturation magnetization in and composition in terms of the atomic ratio of B to A in the formula is a graph showing the relationship between these two parameters for two different rare on coordinates of coercivity in in and composition in terms of the atomic ratio of B to A in the formula RE is a graph showing the relationship between these two parameters for compositions falling along the Ag RE and on coordinates of saturation magnetization in and composition in terms of the atomic ratio of B to A in the general formula RE is a graph showing the relationship between these two parameters for compositions falling along the Ag RE RE Detailed Description The operative compositions are best described by reference to the ternary diagram of 1 wherein the compositions of interest are those falling within the shaded area and which satisfy the RE x is from approximately to approximately The shaded area can be defined in terms of composition by describing X The component of the system or 2 or mixtures of Cu Al and results thus far 3 obtained have been on copper eontaining compositions although a large part of the is retained by 5 total or partial substitution of oopper by and or 6 It has been observed that aton percentages of the 7 may desirably 8 range 2 aton per to 80 atom per sent based on the 9 total of of theae elements together with oobalt 0 1 From the foregoing clearly 2 desirable to utilise as little as possible of a 3 nickel aluminum compound it makes little 4 magnetic contribution to the final composition at usual operating is characteristic that increasing 6 substitution of the oobalt compounds 7 may produce first an increasing and finally decreasing coeroivity while at the same time resulting a 9 decreasing This behavior is evidenced by the 0 Based on such observations and assuming the 1 desirability of high coeroivity together with energy 2 it is possible to define a more preferred 3 range as that which the ratio of B to A approximates the range of from about to about Of 5 other considerations based on specific devloe needs 6 may suggest the use of compositions outside this preferred 7 Whereas formula units for the A and B components has been disouased as a convenient maximum it is evident 9 that these mlxturea are not stoichiometric and that this 0 value be exceeded somewhat while still obtaining the final ooloe of range of compound la to sone on processing Increasing cooling rate the reaction temperature results increasing so lending further credence to the assumption that there is the final a high temperature phase tate at least with respeot to one or the other of the two while the broad Units set forth are desirable in all certain compositional or processing deviations give rise to peak values of ooerelvlty in a aomewhat altered preferred The has bean adequately relies on the retention of pernanent magnet properties in bodies substantially larger than single domain This effect be retained bodies containing a variety of For some oriented samples have been prepared by powdering solid specimens or larger in a matrix such as a wax and orienting within aa applied t la clear that relative amounts of matrix material may be exceedingly permanent magnetic are retained even in bodies in particles are separated by dimension orders of magnitude larger than the While certain additives may be incorporated to modify certain of the magnetic additives of most significance from a or aatitration standpoint have already been set Other may include elements such as iron to increase permeability and elements such aa vanadium to mechanical properties such at unintentional are not generally Nes which or very few weight per cent as well as significantly larger inclusions can have little effect on the structure of the compound the magnetic high energy produot la frequently desirable and since are likely to dilute a preferred compositional range no than 10 weight per cent of additional in solution either or both of the mixed This preferred limit not to any limitation upon the presence of additional phases such as illustrated by a wax Some of the prior work on mixed compounds of the transition metal containing variety have utilised in lieu of a pure rare One variety predominating in cerium costs as little as a few dollars per pound as compared with prices at least in order of magnitude higher for single rare This and other types of mischmetal may be used in the preparation of the inventive It la known from previous work that the orbital roles of the electrons of the rare earths praseodymium and neodymlum make the permanent magnet less the Invention permita suitably high for any of the the resultant increase and in energy produot results in a preference for four Processing It ordinarily desirable to form the solid solution in accordance with a procedure including a rapid over the temperature down to There la no on this Materials the point of about minutes have manifested of 6000 oersteds as with oersteds for the seme processed but with ooollng over the same temperature interval taking place over about one It la considered desirable to utilise a cooling rate of at least per and this considered to be a preferred limit on this processing An obvious metallurgical method useful in the preparation of the materials arc melting and some of the results reported herein were obtained from prepared by this Samples have also been prepared by float zoning and rapid quenching from the liquid Other techniques which permit cooling aa outlined above are The only requirement on processing that reaetlve atmospheric be excluded for the rare earth metal elements form and nitrogen and oxygen should be substantially It has been found convenient to carry out melting an inert atmosphere aa The arc melting method la briefly The desired quantities of elementary materials accordance with the designated are weighed out and The apparatus used consists of a water oooled copper hearth a diameter hemispherical A second also water for of is spaced from the surface of the reactants by a fraction of an inch An arc is struck with a high frequency current amperes or and is a DC to about a 30 total a 30 volt potential at a spacing inch results in a current of about 500 sufficient to in a period of about 30 Cooling the to about io a period of about seconds turning off furnace A has found to result in a substantial While in haa by boating to temperatures as as for e so short have in obtained at for periods of order of at least 4 Higher temperature the in a shorter Annealing be carried out up to about Ti e required for such elevated to realise improvement in is of the order of Peak is in about 30 at and are about 4 hours and to union annealing is not It consistent observation to postulate of phase participation or the invention of properties in of so the for n it fco the or annealed for is to pe orientation be carried at e approaching the Curie u ally of the order of a few hundred degrees In contrast with the prior art single particles so oriented nay subsequently be sintered so as toagain produce a solid Since the magnetic compound is inherently additional processing step may result in a significant in The degree of of depends upon the extent to which single particle sixes are While itis not ordinarily expedient to produce powders as fine as the 10 micron particles previously be desirable to pulverise as snail as about Such pulverised samples represent an advance over prior art single oompound samples that they may be sintered without losing permanent magnet The eoerolvlty and saturation for compounds of the general formula the ratio of B to A varies from sero to are shown in 2 and 3 The and saturation for compounds of the general formula the ratio of B to A varies from sero to above shown in 4 and 5 In each case two curves are In 2 and 4 the curves 2 and 6 describe the eoerolvlty for the compositions as cast whereas curves 1 and 5 the results of the anneal or aging treatment described The improvement obtained as a result of the anneal treatment 3 5 show two Curves and 7 the properties of compounds containing samarium as the rare earth and curves 4 and 8 give the properties of compounds containing cerium the rare gives the properties Tor boundary in of 1 and provides a finn basis for predicting the properties of the included The coercivity of other included compositions are in material after For the value of a magnetic material is treasured in of its This value in is a of the nt of energy can put into an io taken of the product of the B and the coercivity at the of the in the second For the of this in which coercivity is typically than product taken as ia the saturation values for preferred within the inventive ecope are in of a Certain of have had products of 9 inventive materials are primarily by their large coercivity of use in circuitry air include and As contrasted with the the inventive the 1 of in 2 To the 3 larger saturation values available in elements may have 5 normal to the In best of 6 prior art while they 7 of smaller be 8 greater length as to increase the 9 shape 10 The invention been derived in of a 11 of Certain compositional and 12 variations have been others are 13 The invention ia on the retention of single particle properties in bodies of the 15 retention attributed to the inclusion of 16 or in of the listed cobalt 17 She are to be insufficientOCRQuality

Claims (1)

BS4-PT (6-ββ) C L A I M S 31907-

1. A permanent magnet consisting essentially of a composition of matter in which magnetic contribution is primarily due to an intermetallic compound of stoichiometry including (AB) RE in which (A) contains Co or Fe, (B) contains Cu or Ni and RE is at least one rare earth element, characterized in that the energy product of the said magnet is at least one million oersted-gauss, said magnet is in the form of a solid body at le'ast 50 microns in size produced by series of steps including casting, said x is from 5 "to 8.5 * said (RE) is selected from samarium, cerium, gadolinium, praseodymium, lanthanum, yttrium, neodymium and holmium at least 50 atom percent of which is Sm and/or Ce, said (B) is present in amounts ranging from 2 to 80 atom percent based on the total amount of the said (A) and (B) , and said composition is a solid solution of a substantially homogeneous stoichiometry and is within an area on a ternary diagram bounded by lines drawn between the following points: a: 18 percent (A) 71 .5 percent (Β) 10.5 percent Rare Earth b: 16 .7 percent (A) 66.6 percent (Β) 16 .7 percent Rare Earth ' · c: 81 .6 percent (k) 1 .7 percent (B) 16.7 percent Rare Earth d: 87.7 percent (A) 1 .8 percent (B) IO.5 percent Rare Earth. L-B84-PT 31907-2 inc