Rare earths for better magnets

Scientists at Bell Laboratorieshave cast some of the most powerfulsmall magnets ever made ... fromnew materials containing rare earths.The new materials, alloys of cobalt,copper, and samarium or cerium,have the highest known intrinsiccoercive force (field required to re-duce intrinsic magnetization to zero).So, they make excellent permanentmagnets.

It often requires very high mag-netic fields to completely magnetizeintermetallic compounds of sama-rium, cerium, and other rare-earthmetals in certain crystal directions.While iron may require fields ofhundreds of oersteds, and cobaltprobably ten thousand (dependingon grain orientation), compounds ofrare-earth metals may need up to200,000 oersteds. To students ofmagnetism, this indicates a materialof high coercive force.

In practice, however, it is difficultto calculate coercive force accu-rately because the process of demag-netization in these alloys is not wellenough understood. Predictionsare often higher than what is realized.But we do know that very smallgrains tend to produce higher coer-cive force. Also, the better the grainalignment in a favorable magnetic-field direction, the higher themagnetic flux.

By taking a new approachtoward the best grain size and align-ment in pieces of samarium- orcerium-cobalt, E. A. Nesbitt and hiscolleagues at Bell Laboratories pro-duced a magnet having a coerciveforce of at least 28,700 oersteds. First,they combined essentially non-magnetic copper-samarium with amagnetic material, cobalt-samarium,into a new alloy possessing a solidmass of very fine grains. Then by

cooling the melt rapidly in onedirection, they produced long, thincrystals along which desirablemagnetic properties tend to align.Finally, they annealed the material atabout 400° C.

The highest coercive force isreached in a composition rangingfrom Co3 5Cu15Sm to Co3Cu2Sm.Excellent permanent magnets canalso be made by using cerium, whichis cheaper than samarium.

Today, commercial permanent-magnet materials have intrinsiccoercive forces below 5000 oersteds.The high forces achieved in the newmaterials permit practical strongmagnets in small shapes, such asdiscs. Such shapes would be idealfor, say, miniature d-cmotors.From the Research and ©Development Unit ofthe Bell System- Bell Labs

Bioenergetics Bulletin Prospers

vAear ago the hirth of Biocieigerlic,sBulletii w\vas announced (Letters. 15Nov. 1968). Since thein, it has Cil-CLI-lated monthly to ahouLt 250 scicntistsin the United States anId alhiro-lad iftor-mnationt inl the aIrcas of clecti-rol ti-Lilnsfcl-eoxidative phosphoi s lation. photosx n-thesis alnd photosv uthletic phosphors la-tioin, associated enci-0g liniikec tfLnctiolls,biogenesis of mitochodriida aid chloro-plasts. find other related topics. In aId-ditioll to short smLm11ai ics of palpers tobe puLblished, the buLlletill presents in-formiial diSCuISSiOIS an criticism ofconcepts and techniques which mightinot bie appropriate for puLblication inmore formal jouLrnaltls. A Job Mart isone of the newest seivices.

Mlemiibership in this informiiatioll ex-cha.nge group mayli be obtaLined byw niting to mle: tor those liv ing otutsidethe WVesterni Hemiisphere, by writing toR. B. Beechcy, Shell Resea.rch, Ltd..Woodistock AgricuLlturLal Reseairch Cen-tre. Biochemiistry Dixvision, Sitting-hoUrine, Kenit. Eniglaind.

ROBERT E. BELXERLaboratory of C/lze iccil Biology,Department of Zoology,University of Michigan, Auiii Arbhor

Indian Agriculture: Modern

Methods Produce Good lharvests

T. W. Schultz of the Universitv oflChicago (24 Jan., p. 408) believes thatin order to take advantage of recentadvances in agrictultuLral science in In-dia. it will be necessary to shift themain effort to SoLuth India and theGalngcetic plainis.

I u,oLld like to corrcct this impres-sioIn. For the last 7 sears we haxebeen applying the recent adxances toouLr farm of ahotut 25 acr es near Ranichiwhich is not in the above (areas. Therainfall is 58 inches a vear. mostly ill

the monltsooin. TheIe are iarge area,s iCentral India xw ith a similrllr climate andraiin-fall. For irrig.ationl xx tiese oPenwells an dItelectric pumiips. The tenramillis unrstuittable for tube wells. OuLr pro-duction now axvcrages 5000 pOuIIndIs ofrice (tinhLuskecl) aind 4000) pouLnds otwheat per acrc. In additioll. xe ta,ike a

third crop of nmize a.n-d SuLImImIIer r'ice.Ma--Iny of our relationl1s lix e ill Kerla-1L.

a major "rice boxx 1'o' SoLth India.land x heni thex x sit tus thex satxy thexhave niever secn anxthing like oLur pro-ductix itv. The scope ol aglrictultulre in

the plateauL areas is immiiiienise andl. col]dteed the whole of India.. It colI]d heiilcrease.-I CVC]nILirtherbxy SLICh newbtut feasible imiethodis as poly thncn-liiMedra1inwa ter storaue reser oir a pols -thenc daLmIIs hLI i ICC LildlrglrndL be1.Lt)C-ts\eCC Focky oLutci OpS SOotS to blOCkthe pecicolation gap andl raise the x\\ateltable lor opell xelks to jlulnctioll h)Cttci-.Thl.ese alreas haIve advanta. es over thetraditional rice-grow ng lands ot Inldia

the mnain one heiniz a ftreedomi f romHloodls.

1-his kind of farminjg is quitC imIp)S-sihle without suitatble livestock, aIndIhenice there is no needt for any dictarviniballance. RCesults cIn he achie evdsimply by eniergetic aipplication ol thefollowing well-klInowIIntgriCultulIt1I Iprill-ciples. somlc of w hich I nloted Hin mIlCttCl- published 12 J an1Lary 968.

I ) Storage and uttilizatitoni of mloni-sooni rain, hoth sUrfLace and uinder-ground.

2) Correct and IdeCquaIte eCl-tilizer.s.3) Suitabhle high-viclding seecd.4) NIisxcd farming for uItiliza'tion of

waste ,and sLurplus materials anid pro-dLuctioll of manulllre and protein food.

5) Proper uise of pesticides both dlur-ing growth and in storage.

6) Scientific storage land crop drying,equlipnment (this is niot yet avatilahle tols).

Such methods as these and not theblilnd alpplication of mechanical farml-ing aire more apt to solve the foodproblem of dcx eloping couLntries.

RoBEItT B. DAvisBorcva Road, KankA ,

Ranchi-7, Bihlat, I,itliia

Perils of Disease

In his letter (14 Nov.) 0. NI. fMarxasks wh\ the insidles of planiies retulr-n-ing tfronm abroad are sprlaN ed with aniIinsecticide solution, x hich the stew-aridess intfot med hillm wa1s DDT (to thepuhlic, all insecticides cuLrrentl\ aireI)l)T). 1-he lanswer. Of couLse, is to killm(osqti toes. Cspecially /A ophcl.s ioam-liic'. which CaI cat1 ry diseal.ses suLch aisellow tcxcr and malaria into the United

States I). I perfer DDT to xellow'fever-.

TiiomIxs H. JKIFSUnil'nivcrsV of California,BerkelcyA 94720

Reference

1. DL)7) in Hmanian! IVctriiiarv A1 dicWinPiNItlictr- Et. (Blrkha.uci- Vcrtlia, Bastl. 1'959)voi. 2 pp. 370m 461.

SC II\N('[-, V1- it)-,Write for Bulletin S3-600i0A

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OI Stable, flat response, black bodythermopile detector with a one cm2xone steradian total effective field ofview E1 Readout in watts, watts percm2 or watts per cm' per steradianEl Automatically ranges from 10-7watts resolution to 10-1 full scale withprovision for higher range levels EjFixed absolute measurementsorvari-able gain C1 Optional filters, shuttersand irises maintained at thermopiletemperature to maximize stability E]Thermally floating thermopile housingeliminates the effect of ambient tem-perature changes.

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SCIENCE, VOL. 167130 Circle No. 22 on Readers' Service Card