T
USn3/〆
げ)od)
Ulr3
U6Fe
0 100
T(K)
200 300
1'ig.2.'rlleIliernic)e巴ectricPowero「Ulr3,U6「e,Uf'd, alldUSn亀.「orclari竃ylirecurveshavebeenshi「Ied alol覧9吐heordina吐eaxis.
whatlargerthanUleo1herthreecoll1Pounds.
Amongdlespintlしictualinguraniumcom‑
pouuclsofUSn3,UAI2alldUPt,,wellotice SOlllesituilarityintheirtenlperatUre dependenceofTEP.EspeciallythoseofUSi>>
andUAI21ηhavecloserese互11blance;TEPllave positivelargevaluesatroomtemperature.
Near3UKtheychangesighfrompositiveto negativeandhaveanegativepeak.lncaseor UPt3,5,IhesighofTEPisoPPositebuUheこem‑
peraIuredependenceresenlblestotlloseof USn3anctUAlz.RecentlySakuraieta'.18⊃havセ showedei≫piricallythatTfiPofspin[luctua‑
tiollcompoulldslikeMl1Siabovethespillnuc‑
tuatiolltemperaturecanberepreselltedas, S(η=AT+β, where13isaconstanttermreflectingspinIluc‑
tuationenセct.Tlleabovementionedthreecoy≫‑
poundsobeythisequa【ion.Inordertoascer‑
tainUlevalidityofIherulefortllegeneralspin t]uctuatioumaterials,theoreticalsupportand nloreexperinlentalinvestigationarellecessary・
Asanorigillofthelllillhllullla【10wtempera。
Iure,weicanllotdiscardUlepossibilityor phollondragcontribution.Tlletemperatureat Ihe111ini置1,lllll]iswithinUleexpectedtenlpera‑
1990)
50〃7eC/ro"σc'e'"5〃c∫(、 しr'lre77'erg〃oρ'er"・'cρo11・er'〃 .... 3689IncaseorU6FeandU且r3,dleabsolute valuesarerathers>≫all,re(lecli≫gthewic(e bandcharacter.AisoilltheHallelrect measuremellt,s111allabsolutevalueswiIhalit‑
detelnperaturedependencearerePorIedfor bodlconlPounds.2,ForU且r3,UleI111111111U111hl TEPatalowertelllperaωreISPossiblydueto
phonondrageIl℃ct,sillce71min〈7「D/5(T.)is 293KI9り.hlIhesampleofUlr3withsuclla snlallresidualresistivity,wecallnaturallyex。
pectclearphollo置1dragen℃ct.1ncaseorU6Fe, thebroadlnillilnunlcallIlotbeexplainedby dlepllonondragellセcI,since7b/5=25K20}of
【hislnaterialistooIow.The1enlpera1ure100 K≫earwhichTEPs1ar1s【odeviaIefro111Ule 1ｺiglｺtenｺperalureliｺｺeardependenceiscloseto dletenlpera〔ure、vheresomephollollano且11aly llavebeellrePor【edinr>16ssbauere(1'ectand neutron‑dilrractionexperimel11s.2̀ηTha【was attributedtoachallge111tlleelec1runicslruc。
lureoftlleFeatom.20,Sucllachallgecallbe expec吐edtoaPpearalso111TEPexperi置11cllt.
lncaseo『UPd3,i【isinleresIingIosee
、vlletller【heinIluenceofIheitielzsticscaIIer‑
ingamollgcrystalline‑eleclricIielcl(CEF) levelsshowsupin"1'EP.Astrongneutron ellergylosslineIlear14mV(=165K)dueIo
theinelasticscaUei'ingbe1weenCEFlevelswas reportedin1hisco1≫bound.9,Accordin910 TakayanlaandFtllde,ZIｺwccanexpectaTEP
peakat1/30fccrspliUhlgene且 ●gy.The1cn1‑
peralure50KoflhellllllllllU111isjus【closelo dlevalue.
Tlle且owtelllperatureda{aorU6Fealld UPcl3areshown111Fig.3,where、veseesignin‑
cantchangesinTEPrelleclillgsomephase
tranSitiOnSIIltllelOw吐emperaIUre量 ●egiO11.且n
UPd3,thebelldgear6.5KislhoughUobedue toaquadrupolarordering.22,1≫U6Fe,TEP beco置neszerobelowtllesuperconduc1ingtran‑
si【iontemperature.Asisalsosllowllh1Fig.3, thetransitiontenlperaturedecreasesabouI O.35Kundermaglleticl、eldof1T,wllich
agI・eeswithdlerepvrledγ ヒdecrease.ユ))
Tosunlnlarize,TEPofalithenleasured coll1PoundscanIlo〔bedescribedbydleconト binalionor1heshnPledilrusionIel'111andthe phollondragIernLlrrespecdveofdledilrcre11【
itinerancyofSfelectrons,weobserveda
0
̲z
̲4
一6
1
UPd3
V
iIつ乙つーYロコの
( y ≧ ユ ) い
Tにー一4 0
11
、
00Oo
U6Fe
T‑TI
∩V15
0●
000 000000000
0 1
T(K)
30
Fig.3.Thelowtemperalureparlorlllelhernioelec・
吐ricpoweril1UPd,alldU6Fe.置11caseorU6Fe,llle resultsundermagneticfieldofITisalsoshown.Ta and7そarethereportedquaclrupolarorderin9豊emper‑
atureandsuperconductingtemperaturerespectively.
poundwerediscussed.Colllpa置6cdIodlcor。
divaryalldferrolllagllet,thelleavyrermion syslei≫ssucllasUCu5andURu2Sizshowllluch drasticchangesillTEPattheantifer‑
ronlagne【1CIranSlt10nS.
Acklmwledgmen竃s Tllisworkispartiallysupportedbyqlepro。
jestofpriorityareaforthephysicsoiiactinide
● ・
coi≫pouncts,aGrant‑iii‑Aid ResearchfromtheMinistry ScienceandCulture.
)置
)2 ) 3
References
forSciennnc ofEducation,
K.G.GurtovoiandIt.Z.Levitin:Sov,f'liys.‑Usp.
3U(1987)827.
Y.Unuki,"1'.Yamazaki,1.Ukon,T'.Koi≫atsuUara, A.Umezawa,、V.K,Kwok,G.、V.CrabtreealldD.
G.Minks:J.['hys.Soc.Jhn.58(1989)2119.
S.Posse,卜1.S.、VireandE.Callaneo:J.へ 置agll.&
3GgU HideyuklSAroθ'a'.
(Vvl.59,
) 5 ) 6 ) 7 ) 8 )9
lU)
1D 12)
13)
P・WachterancJH.BoPparI(NorIh1‑Tolland, Alns亀erdan1,1982)p.409.
J.J.M.Frallse,A.MeI】ovsky,A.deVisser,C.D・
13redl,U.Gottwick,W.Lieke,E‑1.M.Mayer,U.
Rauchschwalbe,G.SpareandF.S【eglich:Z.Phys.
f359(1985)15.
H.J.vanvial,K.}1.J.BuschowandP.13.van
Aker:771e〃noe'eclr・'c砂'πMρ'α 〃'cCo,置d1,dor5,ed.
F.J.BlaUandP.A.Schroeder(Plenum丑 ⊃ress,New
York,1977)p.1U7.
U.Go賦wick,R.Held,G.Sparl1,F.Steglicli,K.
Vey,W.Assmus,11.Rietschel,G.R.Stewartand A.L.Giorgi:J.・Magn.&Magn.Mater.63&64 (1987)341.
H.Fujii,H.Kawanaka,T."1'akabatake,M.Kurisu, Y.Yamaguclli,J.Sakurai,H.Fujiwara,T.Fujita and1.Uguro:J.Phys.Soc.Jpn.58(1989)2495.
N.Shamir,M.Melamud,H.SIlakedandM.Weger:
Pliysica9413(1978)225.
W.Schlabitz,J.Baumann,B.Pollit,U.
Raucllschwalbe,H.M.Mayer,U.AhlheimandC.
U.13recil:Z.1'lrys.L3G2(1986)171.
E1.R.Utt,f1.Rudigier,E.fielder,Z.FiskandB.
E3atlogg:Phys.Rev.Lett.55(1985)1595.
M.H.vanMaaren,ll.J.vaIIDaal,K.H.J.
E3uscliowandC.J.Scliinkel:SolidSlaleCommon.
14(1974)145.
K.N.Ya巳ig,M.B.Maple,L.E.DeLong,」.G.
HuberandA.Junod:Phys.Rev.X39G989)量51・
14) 15)
16)
17) 18) 19)
2U)
2D 22)
23)
M.R.NormanandU.U.Knelling:1'liysica135[3 (1985)95.
Y.Unuki,T.Yamazaki,1.Ukon,T.Omi,K.
Shibutani,T.KomaIsubara,互.Sakamoこo,Y.
Sugiy<u≫a,R.Onodera,K.Yonei≫itsu,A.
Umezawa,W.K.Kwok,G.W.Ci'abtreeandP.G.
Hinks:Physics14813(1987)29.
Y.011uki,T.Yamazaki,且.Ukon,T.KomaIsubara, 11.Sato,Y.Sugiyama,i.Sakamo10andK.
Yoηelllilsu:J.Phys.(Paris)49(1988)C8‑481.
H.Armbrusler,W.Franz,W.SchlabitzandF.
Steglich:J.dePhys.Co監1.(Paris)40(1979)C4一 量50.
j.Sakurai,Y.YalllamoIoandY.Komura:J.Phys.
Soc.Jpl1.57(1988)24.
M.b.Brodsky,R.J.Trainor,A.J.ArkoalldH.V.
Culbert:1)roc.qズ 〃3e25〃la'」'11'α'co'+f.o'r ハ4⑫re"5川Q'2d痂8'7e〃cA?alerials,ed.」.J.
Becker,G.H.LamderandJ.J.Rhyne(AIP,New York,1976)p.317.
C.W.Kimball,P.P.Vaishnava,A.E.Dwight,J.
G.Jorgensen,andI'.Y.Fradin:Phys.Rev.E332 (1985)4419.
H.TakayamaandP.Fulde:Z.Phys.B20(1975)81.
K.Andres,D.Uavidov,P.Demier,F.}lsu,W.A.
ReedandG.J.Nieuwenliuys:SolidStateCornmun.
28(1978)405.
L.E,Delollg,G.W.Crab【ree,L.N.1tall,H.
Kiersleacl,H.Aoki,S.K.hhar,K.A.Gsclmeider Jr.alldA.Junod:Physica皿35B(1985)8L
、
1
SyｺｺtlieticMetals,20(1987)57‑66
J7MAGNETORESISTANCEOFTHESECOND‑STAGENiC12‑,CoC12‑
ANDCuC12‑GRAPHITEIN'T'ERCALA'T'IONCOMPOUNDS
1.SlilOZAKI*andT.FUKUIiARA
Depart'ne'ltoブ 」P'1ンSICS,Facultンo!Sc'e'盈ce,To'〜 ンoMetropolita'1U'ii【 ノersit;ソ,Tokyo158
(」叩 ω り
M.SUZUKI
DepαrごmeritofP'sンs'cs,StateUniversityof1>eωyorた,β 加gleanlon,1>Y13901(σ.S.淘 1.OGURO
1'1Sごitute1「orSo"dSご α'eP'1ys'cε,U'iiversitンoプTohンo,Toた1ソ0106で 」αPα'1♪
(ReceivedAugust12,1986;acceptedNovember6,1986)
Abstract
Themagnetoresistanceofthesecond‑stagegraphiteintercalationcom‑
poundsofMC12hasbeenmeasuredinthetemperaturerange1,4‑30Kand lllmagneticfieldsupto10kOe.Here,MisolleofNi,CoorCu,andthehost materialissingle‑crystal(DISH)graphite.Allthecompoundsshoweda negativemagiletoresistance,whoseminimumisdistributedaroundafew hundredOe.Theexistenceofnegativemagnetoresistallcesuggestsaconsi・
derablecolitributionofthemagneticscatteringfromtheintercalantstothe conductionelectrons.Ithasbeenconcludedthatthedominantoriginsof thenegativemagnetoresistancecomefromthesuppressionofinagnonor spindisorderscatteringbythemagneticfield,and/orfromthespinflop process.Thecompetitionbetweentinedifferentanisotropyofeffective fields,thedifferenttransitiontemperaturesandthedifferentspinflopfields givesrisetoavarietyofbehavioursindifferentsamples.
Introduction
SincetheearlyworkbyKarimov【1‑3】,themagneticpropertiesof graphiteintercalationcompounds(GIC)of3dtransitionmetaldichlorides haveueenstudiedbymanyauthors【4・14].Becauseofthesandwich‑1ike structureofinagileticandnon‑magneticlayers,themagneticpropertiesin
thosecompoundsarehighlyanisotropic.Themagneticlayersinthosecom‑
poundsareknowntohaveanislandstructurewithmeanislanddiameters oftheorderof100A.ThefillingcoefficientsusuallyrangebetweenO.9and
*AuthortowhomcorrespondenceshouldUeaddressed .
58
0.7wllelltheBostmaterialsaresinglecrystals[4].Suchaniil‑planestruc‑
Luregivesacharacteristicmagneticbehaviour.Ithasbeenobservedthat NiC12‑allciCoC12‑GICsshowamagneticpleasetransitionattwosuccessive temperatures,whicharedescribedasTauandTel,respectively.Thehigher temperaturepllaseatT>7Cuisparamaglletic.Theintermediatephase betweellTCuandTclistwodimensiona1(2D).IthasIIOspontaneousmagne‑
tizationasawhole,butisunstableandchangestoaferromagneticstateinan appliedmagneticfield.ThelowtemperaturephasebelowTelhasthree‑
dimellsional(3D)order.ThemetalIOIISintheintercalantareferromagnet‑
icallycoupledalongthec‑planeofthecrystal,andthelayersareantiferro‑
magneticallycoupledalongthec‑axis.Theantiferromagneticspinflopfield, IIF,一,isalsoailisotropicantiismuchreducedcomparedwiththepristine
trailsitiotlmetalciichloricie.
Suzukieial.[5,6]measuredthemagneticsusceptibilityofNiC12‑and CoC12‑GICsinfieldsalongthetwoindependentcrystalaxes.Theydeter‑
minedTCuandTc1,andestimatedanisotropyparanletersincludingthespin flopcriticalfieldsparallelantiperpendiculartothec‑axis,HFiiandHFI.
Suematsuetal.【7】measuredthemagnetizationofwell‑stagedsamplesof NiCl2‑GICpreparedfromsyntheticsinglecrystals(KISH)ofgraphite,alid determinedCuandTclandmagneticparametersinfieldsalongthehexag‑
ollalplane(c・plane).Oguroetal.【81measuredthefielddependenceof magnetizationat4.2KinNiC12‑andCoC12‑GICsinfieldsparallelandper‑
pendiculartothec‑axis.Theyobservedastrongmagneticanisotropyin CoC12‑GIC,w}iiletheanisotropyinNiCl2‑GICwasratherweak.
InCuCl2‑GIC,ontheotherhand,theintraplaneinteractionistwo‑
dimensionally[10]orone‑dimensionally[11]antiferromagnetic.Il,ancourt etal.[10]measuredthemagneticsusceptibilityofthesecond‑stagecom‑
poundsofCuCl2intercalatedintofourtypesofhostmaterials:natural graphitecrystals,HOPGandpitch‑basedfibreswithtwodifferentorienta‑
tions.Theysuggestedthatthree‑dimensionalorderingdidnotoccurdownto 1.9Katleast.Thespinflopfieldwaspredictedtobehigherthan41kOe, wliicliisattributedtothepristineCuC12.Thec‑planewastheeasyplaneof magnetizationbelow16K.Theyalsoshowedthatthetemperaturedepen‑
deuceofthemagneticpropertiesdependsonthesizeofislandsandonthe fillingparameter.Nishiharaetal.【11】lneasuredtlletemperatureandthe stagedependencesofthemagneticsusceptibilityinCuC12‑GICinfieldsalong t}lec‑axis.Inthefirst‑stageCOIllpOUnCISwithsinglecrystalKISHgraphite, theysuggestedthepossibilityofthetyvosuccessivemagnetictransitions similartothoselilNiC12‑andCoCl2‑GICs,buttheoccurrenceinthesecond‑
stagecompoundshasnotbeenestablished.Summariesofthemagnetic propertiesinthiskindofcompoundaregivenbyIkeda[12]andMatsuura etal.[13,14].Severalparametersobtainedpreviouslyaresummarizedin Table1.
Iftheconductionelectronsmoveunderanymagneticinteractionwith theintercalants,thetransportpropertiesshouldreflecttheabovemagnetic
59
TABLEl
ParametersIllthesecond・stageNiC12‑,CoC12‑andCuC12。 ピraPhiteintercalationcom・
pounds.TCIandTauaretheloweranduppermagnetictratlsitiontemperatures,respec‑
tively.HF汐andHF⊥arethespinflopfields121theantiferromagneticphaseofeverymate・
rial,where//and!refertothecrystalc‑axis
Iiiter‑
calant
Lostmaterial Spinflopfields (Oe)
Transition temperatures(Kj
1礼eferellce
HFI/ HF⊥