简介:ThepolycrystallinesamplesofLa2/3Ca1/3MnO3werepreparedbyaconventionalsolidstatereactionmethod.Themagnetizations(ZFC,FCandinitialmagnetization)ofthepolycrystallineLa2/3Ca1/3MnO3weremeasuredwithsuperconductingquantuminterferencedevicemagnetometer.Thescalingtheorywasemployedtostudythechangesofcriticalbehaviorarisingfromtheappliedexternalfield.Thecriticalparameterβdecreaseswithincreasingtheexternalmagneticfieldresultsinanincreaseinthemagnitudeofferromagneticordering.
简介:Melt-spunribbonswhicharetheimportantrawmaterialforhot-deformedmagnetscanbepreparedbysingle-rollermelt-spinning.Inordertopreparewell-structuredribbons,themodeloftemperaturefieldforsingle-rollermelt-spinningprocesswasconstructedinthiswork.Theheatconductioninthisprocesswassimplifiedasonedimensionalheatconductionproblem.Itwasshownbymodelingthat,thetemperaturefieldinthemelt-spinningbeforesolidificationinthismodelcouldbedescribedasthisequationT(x,t)=Tmoexp[–k(x–x0)–k2αt]+T0.ThetemperatureT(x,t)ofthealloymeltsdecreasedwithincreasedpositionxandcoolingtimetexponentiallyfromthewheel-freesurfacetothewheel-sidesurface.TheconstantkdeterminedthedecreasespeedofalloytemperatureT(x,t),whichwasproportionaltotheinterfacialheattransfercoefficienthandtheinterfacialareaofheatconductionA0,butinverselyproportionaltothethermalconductivityK.x0wasthethicknessofthealloymelt.Withincreasedx0,thetemperaturedifferencebetweenwheel-freesurfaceandthewheel-sidesurfacebecamelarger,whichwouldleadtolargerdifferenceingrainsize.Inexperiments,theinfluenceofmelt-spinningprocessparametersonthetemperaturefieldmodelwasdiscussed,suchascoolingrollermaterials,wheelspeed,andsoon.Melt-spunribbonspreparedbysingle-rollermeltspinningatdifferentwheelspeedwereinvestigatedandmagneticpropertiesofdie-upsetmagnetsfrommelt-spunribbonsondifferentcoolingrollerwereanalyzed.Thevariationofgrainsizeinthedepthdirectionconsistedwithtemperaturefieldmodel.Thismodelprovideddirectionsforthepreparationofmelt-spunribbonswithuniformlydistributedfinegrains,whichwereverynecessaryforproducinghot-deformedmagnetswithhighmagneticperformance.
简介:Afacilecatalysis-freemethodwasutilizedtosynthesizefunctionalneodymiumhexaboride(NdB6)nanowiresofsinglecrystalusingNdpowdersandBCl3asstartingmaterials.TheXRDpatternconfirmedthatasinglephaseNdB6couldbeobtained.Raman-spectraelucidatedtheactivevibrationalmodesofthehexaborides.TheTEMimagesclearlyshowedthatthehexaboridesweresubmicroninsizewithacubicmorphology.Thefieldemissionoftheseone-dimensionalNdB6nanowiresshowedalowfieldemissionturn-on(5.55V/μmatacurrentdensityof10μA/cm2),andhighcurrentdensitywithafieldenhancementfactorof1037.TheemissioncurrentdensityandtheelectricfieldfollowedtheFowler-Nordheim(F-N)relationship.Thegoodperformanceforfieldemissionwasattributedtothesingle-crystallinestructureandthenanowiregeometry.
简介:一系列新奇的镧锶铝酸盐黄磷,Ce3+-dopedLaSr2AlO(5-0.5x)Fx(LSAF)黄磷成功地在减少空气下面用高温度的稳固的州的合成过程被综合(H2/N2=1/4)。X光检查衍射模式表明那件LSAF样品是纯LaSr2有1250的sintering温度的AlO5阶段?桰獯桰牯?祢挠湯牴汯楬杮挠祲瑳污映敩摬攠癮物湯敭瑮眠瑩?汦潵楲敮椠湯?猼灵?猯灵>
简介:Au/TbMnO3/YBa2Cu3O7-xcapacitorswerefabricatedonSrTiO3substratesbypulselaserdepositiontechnique,ofwhichelectricpropertieswereinvestigatedinthetemperaturerangefrom25to300K.Bothcurrent-voltagecharacteristicsandjunctionresistanceswithbiasvoltagesshowedremarkabletemperaturedependence,inwhichobviousthermallyexcitedrelaxationprocesseswerefoundbetween150and200K.Atthetemperatureslowerthantheactivationprocess,theleakagecurrentsofthecapacitorswerestudied.Interestingly,athighelectricfield,themechanismoftheleakagewasPoole-Frenkelemission.However,atlowelectricfield,theconductionwasnotOhmic,andideallnJ∝E1/4characteristicswereobserved.Analysisshowedthatthepossibleoriginwasrelatedtotheinherentinhomogeneousnatureofactivationlesspercolatingtransport.
简介:Thephasesandmagnetocaloriceffectinthealloys(Gd1-xErx)5Si1.8Ge2.2withx=0,0.1,0.2and0.3wereinvestigatedbyX-raydiffractionanalysisandmagnetizationmeasurement.ThesamplesweresinglephasewiththemonoclinicGd5Si2Ge2-typestructure.WiththeincreaseofErcontent,theCurietemperature(Tc)decreasedobviouslyfrom253Kofthealloywithx=0to114Kwithx=0.3.Themaximummagneticentropychangedinthesamplesof(Gd1-xErx)5Si1.8Ge2.2withx=0.0,0.1,0.2and0.3were6.88,8.32,9.59and10.24J·kg-1·K-1respectivelyintheappliedfieldchangeof0~2.0T.
简介:Theeffectofanexternalelectricfieldonthecrystallizationbehaviorofamorphous(Nd0.1Fe0.9)3Balloywasinvestigated.ThecrystallizationproductofNd2Fe23B3phasewasobtainedforthisamorphousalloyannealedat923Kfor300sinthepresenceofanexternalelectricfieldof300kV·m-1(50Hz);whilethecrystallizationproductsareNd1.1Fe4B4,α-Fe,andFe3Bphasesunderthesameannealingconditionexceptforfree-electricfield.Ontheotherhand,thesampleswereannealedat1023K,whichishigherthanthedecompositiontemperatureofmetastableNd2Fe23B3phase,for600s.Inthecaseofthepresenceofanexternalelectricfield,themetastableNd2Fe23B3phase,asamainphase,isstillstayedinthesample.ThisfactsuggeststhattheexternalelectricfieldenhancesthestabilizationofthemetastableNd2Fe23B3phase.Theeffectoftheexternalelectricfieldonthephaseselectionandstabilizationwasexplainedintermsofthespecificconductancedifferencebetweenthecrystallizationproducts.