Volume85A, number6,7 PHYSICSLETFERS 12 October1981

REENTRANT SUPERCONDUCTIVITY IN Tm2Fe3Si5

C.U. SEGREandH.F. BRAUN1

Institutefor PureandAppliedPhysicalSciences2 Universityof California,SanDiego,La Jolla, CA 92093, USA

Received22 June1981

Resistivityandac susceptibilitymeasurementson Tm2Fe3Si5show theonsetof superconductivityat 1.7 K which is

destroyedat 1.13 K. Similar resultsareobtainedin solid solutionsof (Tmj ~xLux)2 Fe3Si5.

The competitionbetweensuperconductivityand in a purifiedargonatmosphere.Theingotswerethenlong-rangemagneticordermanifestsitselfin a number sealedin quartzcapsulesundera partial pressureofof rare earth(RE) ternarycompounds.This interplay argon,homogenizedat 11500 C for four daysandresultsin thephenomenaof reentrantsuperconduc. annealedat 800°C for eight days.Phaseanalysiswastivity [1—51andcoexistenceof superconductivityand performedby X-ray powderdiffractometryusingCrantiferromagneticorderwith themagneticordering radiation(2.2909A). The samplesare essentiallytemperaturebothabove[6] andbelow[7] the super- single-phaseSc2Fe3Si5typecompounds.Theinte-conductingcriticaltemperature.In particular,ErRh4B4 gratedintensityof the impurity linesamountsto lessbecomessuperconductingat 8.7K andentersa ferro- than 0.1%of thetotal diffractedintensity.Thepuritymagneticallyorderedstateat 0.9 K which is respon- of the samplesisconfirmedby photomicrographicsible for the destructionof superconductivityat Tc2 analysiswhich indicatesthatany secondaryphasescon-[I]. Among all the compoundswhich exhibit suchre- stitute lessthan 1 vol% of thematerial.The low-fre-entrantbehaviour,only ErRh4B4 andH0M06S8 [2] quency(20 Hz) acsusceptibilityof all the sampleswascontaina spatiallyorderedsublatticeof REatoms.In measuredandthe resistivity of abar-shapedspecimenthis paper,we reportthe occurrenceof reentrantsuper- of Tm2Fe3Si5wasmeasuredusinga four-leadtech-conductivityin Tm2Fe3Si5, the third reentrantsuper- nique.conductorwith anorderedREsublattice.The The resistivityof Tm2Fe3Si5decreasesmonoton-RE2Fe3Si5 structureforms with therareearthsSm, ically from roomtemperatureuntil it reachesits re-Gd—Lu, and Sc,Y [8,9]. The compoundswith RE sidualvalueat about10K wheretheresistivity ratio= Lu, Y, Sc are superconducting[9] while thosewith p(300K)/p(10K) approximatelyequals20 indicatingRE= Gd—Er orderantiferromagnetically[10,11]. a well-crystallizedmaterial(fig. 1). At 1.7 K the resis-Mässbauerstudiesshowthat the Fe atomsin boththe tivity dropshalfway to zero andthenreturnssharplytosuperconductingandantiferromagneticcompounds its previousvalueat 1.1 K. This maybeinterpretedcarryno magneticmoment[10,12]. asthe onsetof superconductivitywhich is destroyed

All sampleswere preparedfromhigh-purity ele- at the lowertemperaturebeforethetransitionis com-ments(RE: m3N;Fe: m5N; Si: m7N)by arc melting plete.By itself, however,this resultdoesnot conclu-

sivelyshowthatTm2Fe3Si5isa reentrantsupercon-1 Presentaddress:DépartementdePhysiquede la Matière ductor;therefore,a studyof thepseudoternary

Condensée,Universitéde Genêve,1211 Geneva4, Switzerland. (Tm1 —xLu~)2Fe3Si5 systemwasundertakento clarify2 Researchsponsoredby theNationalScienceFoundation thebehaviorof thepureTm compound.

undercontractNSF/DMR7708469. Theac susceptibilityof 11 sampleswith 0 ~ x ~ 0.20

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Volume 85 A, number 6,7 PHYSICS LETTERS 12 October 1981

TEMPERATURE,K

Fig. 1. Resistivity of TmzFeaSis.

yields three pieces of information (fig. 2). First, the size of the diamagnetic transiton increases with in- creasing x until at x = 0.10 the transition is com-

1.0 2.0 3.0

TEMPERATURE, K

Fig. 2. The ac susceptibilities of (Tml -xLux)zFesSis com- pounds for 0 < x < 0.2. The curves are shifted vertically for clarity.

plete by 1 K, the lower limit of the measurement. Second, the transiton at the lower temperature for the samples with x < 0.07 is uniformly sharp, its width being less than 50 mK. The sample with x = 0.10, when measured down to 0.4 K shows a similarly sharp second transition at 0.95 K. Finally, below the lower transi- tion, the ac susceptibility once again decreases, a be- havior also seen below a magnetic ordering temperature and, for example, below Tc2 in ErRh4B4 [ 11. When these data are plotted as a function of x (fig. 3), the ex- istence of reentrant superconductivity is apparent. The sample with x = 0.10 shows a complete superconduct- ing transition followed by a superconducting-to-mag- netically ordered transition. The continuous progression in the ac susceptibility data from x = 0.10 to x = 0 in- dicates that in the pure Tm2 Fe& there is an onset of superconductivity at 1.70 K but the transition is not complete when it is destroyed by magnetic ordering at 1 .13 K. This is the behavior observed at the critical points in the pseudoternary systems (ErI_,HoX) Rh4B4(xcr=0.S9) [31a~d(~~_xH~x)W4~4 (xcr = 0.92) [ 131. Further measurements, such as specific heat or dc susceptibility, would be useful in confirming the occurrence of reentrant superconductivity.

To date, all reentrant superconductors with a crys- tallographically ordered lattice of rare earth atoms show ferromagnetic ordering. Thus, ferromagnetic or-

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Volume85A, number6,7 PHYSICSLETTERS 12 October 1981

3 I I I resistivityof Tm2Fe3Si5.Onepossiblecausecouldbe

theonsetof superconductivityasis observedin Ho(Tm1,Lu,)2Fe3 Si5 somekindof short- or long-rangemagneticorder above(R~~1i_xhx)4B4[6].

~ 2 - - The observationof reentrantsuperconductivityinuJ J Tm2Fe3Si5andthe pseudoternarysystem

I— t (Tmi~Lu~)2Fe3Si5posesanumberof questions

~ ftLLT Iii~ abouttherole of iron andthenatureof the statewhichI - destroyssuperconductivity.Experimentstoresolve- thesequestionsareunderwayandwill bepublished

elsewhere.

Thiswork is dedicatedto thememoryof ProfessorC I I I I

0 0.1 0.2 B.T. Matthias.MOLE FRACTION , X

ReferencesFig. 3. Partialphasediagramof thepseudoternary(Tm

1 .xLux)2Fe3Si5 systemfor 0 ~ x ~ 0.2. Thebarsre- [1] W.A. Fertig etal., Phys.Rev. Lett. 38 (1977)987.presentthewidth of thesuperconductingtransitions,Tci. [2] M. Ishihawaand0. Fischer,Solid StateCommun.23Thecirclesshowthemidpointsfor thosesamplesin which the (1977) 37.superconductingtransitionis completeandthesquaresmdi- [3] D.C. Johnston,W.A. Fertig, M.B. Maple andB.T.catethereentranttransitions,T~. Matthias,Solid StateCommun.26 (1978)141.

[4] J.P.Remelkaetal., SolidStateCommun.34 (1980)923.[5] B.C. Ku and R.N. Shelton,Bull. Am. Phys.Soc.26

(1981)342;andto bepublished.

deringof theTm momentscould beresponsiblefor the [6] H.C. Ku, F. Acker andB.T. Matthias,Phys.Lett. 76A

destructionof superconductivityin Tm2Fe3Si5and (1980)399.[7] R.W. McCallum,D.C. Johnston,R.N. Shelton,W.A.thesolid solutionswith Lu2Fe3Si5.However,it has Fertig andM.B. Maple,Solid StateCommun.24 (1977)

recentlybeensuggestedthatantiferromagnetismmight 501.

be responsiblefor the destructionof superconductivity [8] 0.1. Bodak,B.Ya. Kotur, V.!. YarovetsandE.I.

in Dy(Rh1—x Ru~)4B4nearthecritical concentration, Gladyshevskli,Soy. Phys.Crystallogr.22 (1977)217.Xcr = 0.33 [14]. Furthermore,sincetheRE2Fe3Si5 [9] H.F. Braun,Phys.Lett. 75A (1980)386.[10] H.F. Braun,C.U. Segre,F. Acker andM. Rosenberg,tocompoundswith RE = Gd—Er all orderantiferromag- bepublished.netically, thequestionaboutthenatureof themagnet- [11] A.R. Moodenbaugh,D.E. Cox andH.F. Braun,Bull.ic orderingwhichdestroyssuperconductivityin Am. Phys.Soc. 26 (1981)468; andto bepublished.Tm2Fe3Si5is stifi open. [12] J.D.Cashion,G.K. Shenoy,D. Niarchos,P.J.Viccaro

A smallmaximumis observedin theacsusceptibil- andC.M. Falco,Phys.Lett. 79A (1980)454.[13] M.B. Maple, B.C. Hamaker,D.C. Johnston,H.B. Mackayity of eachof thesamples(fig. 2) at approximately andL.D. Woolf, J.LessCommonMet. 62 (1978)251.2.6 K, well abovetheonsetof superconductivity.At [14] B.C. HamakerandM.B. Maple, in: Proc.XVIth Intern.

the sametemperature,amaximumis alsovisible in the Coni.on Low temperaturephysics(1981),to bepublished.

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