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1 Engineering Nte E»A22 rag Electrnic Cmputer Divisin Servmechaniuma Labratry Masachuset.tr. Institute f Technlgy Cambridge), Massachust.1 SUBJECT: T: Frm: RECTANGULAR-LOOP MAGNETIC CORE MATERIALS N 0 H 9 Taylr W. N 0 Papian Date: September 4, 1951 Abstract: There are ferrmagnetic cres n the market tday which are suitable fr use in high-speed multi-dimensinal strage arrays and in fast stepping registers,, Testa mad-r; here indicate the high prmise f Armc M-Pentalj.y-216, a metal, and Ferramlc A, a ceramic,, Gradual imprvements in the characteristics f pertir.ent cre materials are expected t cntinue. A, INTRODUCTION Three general classes f ferrmagnetic materials are n the market tday,. They are: 1. Metallic materials 2. Ceramic materials 3. S-called pwder r dust materials The last mentined class will nt be discussed here because pwder cres cannt nw be made which cmbine rectangularity characteristics alng with reasnable freedm frm eddy-currents The metallic and ceramic classes bth ntain pertinent and prmising materials fr applicatins which require rectangular B-»H lps and the freedm frm eddy-currents which allws quick changes f magnetic flux t ccur,*»2» 1. W N Papian, "Ferrmagnetic Materials fr Applicatins Requiring Rectangular Hysteresis Lps and Shrt Respnse Times," M.I T 3 E f E a Seminar Paper, Jan W N 0 Papian, W A Cincident-Current Magnetic Memry Unit,," Prject Whirlwind Reprtfizl22,M.I.T., August 1950

2 6345 Engineering Nte E-422 Page 2 B 0 METALS Fr the particular purpses f the grup wrking n.tagneticcre strage at this Prject nly ribbn-wund ring-shaped crue have been f significant interest in the metallic class. The materials will be discussed in a mre r les3 chrnlgical rder, that is,, in the rder in which they came v t ur attentin,, 1 0 Deltamax This material is a grain-riented, 50% nickel-irn ally made by the Allegheny-Ludlum Steel Crp. and marketed in special shapes by a subsidiary, the Arnld Engineering C. Deltamax has en extremely rectangular B-H lp (see Fig. 1) very lw cercivity, high maximum-flux density and lw resistivity; it is available in ribbn thicknesses as lw as la mil. Interest in Deltamax is lw here largely because f its extremely lng switching times under lw and medium excitatins, and because f the large percentage f input energy which is lst in eddy currents under high excitatins. As an example, a Deltamax cre made f 1-mil ribbn takej f the rder f 5 millisecnds t reverse its magnetic flux under an excitatin which is abut twice its cercivity. The same cre can be switched in abut 40 micrsecnds, but it requires an excitatin value abut 10 tiaes its cercivity. 1-mil Deltamax is the material nw being used in the Harvard, Alden, Wang, and Burrughs stpping-register (Static Magnetic Delay Line) cres 2. Sllectrn This is the familiar Jf> silicn-irn ally knwn as electrical sheet, but with a partial grain and dmain rientatin prduced fr us by Allegheny Ludlum. It has the very rectangular B-H characteristic shwn in Fig,, 2. Cercivity and maximum-flux density are high resistivity is lw and the material was available t us in the 1-mil thickness, The very successful metallic cre used in the early experiments and the cres used in the experimental 2x2x1 array were m*d«f this material* Resultant eneeda were pd (abut 20 micrsecnds with a 2tl slatia rati) and sl nal ratis mra very high. The main disadvantage f Sllectrn is the high cercivity which calls fr high driving ampere-turns, and the rather high switching energy as Indicated by its large B-R lp area. Sllectrn was the mst prmising metal until a few mnths ag when the material t be discussed belw appeared n the scene 0

3 n - ' -I -. - T" i nri TAKiiAv u. '" IC lb. 14 i H 2 _ 19 m - A (B) - fi I O ;SES -. 4 e> i KILO -. 9 C OE RSTE DS ( -H) i. 3 J > j> * H C OERSTEDS (H) / > J S A i.«> C SCALE CHANGE 6X. 4 SCALE CHANG 5x _ a _ Q 10 OD UJ < </> - r> < 1 - *% H THE ARr IOLO ENC JINE ERINi s a ). I CO < CHICAGO, ILLINOIS FIG. 1

4 I: Ki I l 0> 00 t FIG. a

5 6345 Engineering Nte E-422?age 5 3e M-Penpally-216 M-Permally-216 is Armc Steel Crpratin's special versin f that 79? nickel, l& mlybdenum irn ally. They btain the gd rectangular B-H lp shwn in Fig. 3 by a special magnetic anneal 0 Cercivity and maximum flux density are lw, resistivity average, and it is available in thicknesses dwn t l/6 mil 0 Interest in M-Permally-216 is high; it has virtues fr applicatin either as a cincident-current unit in a multi-dimensin*.! array r as a memry unit In a stepping register. M-Permally-216 cras switch rapidly at all excitatins due In part t the fllwing characteristics< availability f extremely thin material, lw flux densities nt-t-high maximum-differential permeabilities, and an apparent freedm frm fractinal-secnd lags in magnetizatin at very lw excitatins. The small lp area als accunts fr the lw switching energies required. Small cres f this material will be used in the 16 x 16 array nw in design. They are als being cnsidered by urselves, and by Burrughs at ur urging, fr use in faster, ltier-energy versins f the stepping register* The material is relatively new s that prductin and unifrmity difficulties are being experienced by ur cre supplier, Magnetics, Inc., and by thers,. There is, hwever, perfectly reasnable expectatin that these difficulties will be Irned ut in a shrt time. C. CERAffCS Where fractinal-micrsecnd switching tiitas are needed, the metals in their present frm are unsuitable, largely due tc eddy currents. The develpment during this last decade f a grup f semi- Insulatr ceramics which have ferrmagnetic characteristics answers the abve need. These materials are called magnetic ferritin by sme and ferrsplnels by thers. They are hmgeneus cmpunds f varius metal xides (nt metals) with resultant mechanical prperties resembling thse f dry-prcess prcelain. In general the ceramic materials have lw B«H rectangularity, high cercivities lw flux densities, but phenmenally high resistivities. Quite a few materials have been cnsidered, but nly tw are wrth mentining,,

6 -iu»», a L jii. D-C HYSTERESIS LOOP CORE NO. 216 UJ CO CO z> < z OD Q 79-4 PERMALLOY I 0.26 MILS 1/4 WIDE l'/ 2 I.D. WOUND ON CERAMIC SPOOL B r * 1 =0.85 ii >-B m =7.90 at H m 1 t 1 " m O X 1 4. t mix <J <J i z 0 H C = 0.I H-OERSTEDS TT =0.915 fr B m =7.45 t CD CJ O in i CURVE NO ARMCO RESEARCH LABORATORIES _ FIG. 3 *

7 6345 Engineering Nte E-422 Page 7 1, Ferrxcube IV This material was the first ceramic t exhibit any rectangularlty. Hwever, it did s t any marked extent nly when it wac under sme applied mechanical strain. Because f this, and its at-tc* high resistivity, interest in it waned early. 2. Ferramlc A Ferramic ia the smart trade name which the General Crramica and Steatite Crp. gives t its magnetic ferrites c Althugh there are nearly ten different Ferramics, nly the A material has thus far shwn sufficient rectangularlty t perate as a cincident-current memry unit 0 This material has a B-E lp shape as shwn in Fig:, &. Cercivity is high and maximum flux density lw, even relative t the ther ceramics Its resistivity ie extremely high, and it appears t have n significant magnetizatin time lags in the micrsecnd regin c Interest in this material is als high. It is a ptential candidate fr use in high-speed multi-dimensinal arrays and stepping registers. Imprvements in the material's characteristics are desirf.ble in the tw directins f lwer cercivity (reduced driving ampere«*tuvns) and better B-H rectangularlty. It is als desirable, but difficulty t get cres made in very small shapes and sizes. Develpment wrk in tbaca and ther directins is ging n and is being encuraged by the labratry. Sme slightly imprved versins f this cre material have been received and tested, and ther imprved samples are expected in the future 0 Ferramlc A cres have been perated here as cincidentcurrent units with 2:1 and 3:1 selectin ratis at switching speeds f abut 1/2 micrsecnd. They have als been perated by Buck and Gi?dltz In a A-cre stepping register at speeds ver 100,000 digit-transfers per secnd using utsize cres and ther parameters nt truly ptimized fr the jb. D 0 CONCLUSION Presently available rectangular-lp ferrmagnetic cres fr high-speed strage and pulse applicatins cntain a few which shw a great deal f prmise. Arm"s H-Permally-2l6 is, at the mment, the mst interesting amng the metals; the mst prmising ceramic is a slightly imprved Ferramic A cre. Bth materials are useful as they stand, and cntinued imprvements are expected. Signed»*iJflJl \^> E?~* W. N. Paplaa WHP:lrt Apprved by Drawings Attached: Fig 1 - Drawing K e A G, Page 3 Fig. 2 - Drawing N A-3P999-0, Page U Fig. 3 - Drawing N A-50265, Page 6 Fig. A Drawing N SA-50264, Page 8

8 - -;if <*. SKETCHED FRO/V CP5C/i.LO*-MPHlC PRESENTATION AT (,0^ (H) P BCRVOMIXHANISMS LABORATORY OF THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY DIVISION OF INDUSTRIAL COOPERATION PROJECT NO. B-H LOOP SHAPE - IMPROVED FERftAMIC A ORE #/ SCALC: n. &u, ENG. D W. CK. AFP. SA-S"OZ<^