LowTemperature Magnetic Properties of Co Antidot Array文献翻译文档格式.docx

LowTemperature Magnetic Properties of Co Antidot Array文献翻译文档格式.docx

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LowTemperatureMagneticPropertiesofCoAntidotArray文献翻译@#@Low-TemperatureMagneticPropertiesofCoAntidotArray*@#@@#@Cobaltantidotarrayswithdifferentthicknessesarefabricatedbyrfmagnetronsputteringontoporousaluminasubstrates.Scanningelectronmicroscopyandgrazingincidencex-raydiffractionareemployedtocharacterizethemorphologyandcrystalstructureoftheantidotarray,respectively.Thetemperaturedependenceofmagneticpropertiesshowsthatinthetemperaturerange5K--300K,coercivityandsquarenessincreasefirstly,reachtheirmaximumvalues,thendecrease.Theanomaloustemperaturedependencesofcoercivityandsquarenessarediscussedbyconsideringthepinningeffectoftheantidotandthemagnetocrystallineanisotropy.@#@PACS:

@#@75.75.+a,75.50.Cc@#@Periodicantidotarraysconsistingofnonmagneticholesincontinuousmagneticfilmshaverecentlyreceivedmuchattentionbecauseoftheirpotentialadvantagesovermagneticdotsystemfordatastorage.[1]Recentmicro-magnetizationcalculationshowsthatitsarealdensitiesapproach750Gb/in2.[2]Moreover,theadvantagesoftheantidotarrayincludenosuperparamagneticlowerlimittothebitsizeandthepreservationoftheintrinsicpropertiesofthecontinuousmagneticfilm.Acommonmethodtofabricatetheantidotarrayfilmistopatternthecontinuousfilmusingelectron-beamlithography[3-5]orfocusedionbeammilling.[6]However,thesemethodsaredemonstratedperfectonlyforsub-micronantidotarray.Astheantidotsizedecreasestonanometer,interestingbehaviourmaybeexpected.Inparticular,reducedantidotsizecanresultinchangesofdomainstructure[7]andwillaffectthemagnetizationreversalofthefilm.Oneoftheothermethodstofabricatethenanometerantidotarrayisdepositingmagneticmaterialontoaporousaluminasubstrate.[8]Usingthismethod,theantidotsizeiseasilycontrolled.Untilnow,themagneticpropertiesofNi[8]andCoFe,NiFe/Cu/CoFe[9]antidotarrayfilmsonaluminasubstrateshavebeenstudied.However,themagneticpropertiesatlowtemperatureofCoantidotarrayfilmsarestillopen.InthisLetter,weinvestigatethestructureandtemperaturedependencesofmagneticpropertiesofcobaltantidotarraysfabricatedbymagnetronsputteringontoporousaluminasubstrate.@#@TwoprocedureswereusedtofabricateCoantidotarrayfilms.Firstly,porousaluminasubstrateswerefabricatedbyatwo-stepoxidizationprocedureasdescribedpreviously.[10]Afterthesecondoxidization,theresidualaluminumwasremovedbyasaturatedHgCl2solution.Secondly,antidotarraysweredepositedbyrfmagnetronsputteringfromacobalttargetatroomtemperature.Thedepositionratewasabout1.5nm/min.Thesputteringchamberwasfirstlypumpeddownto2.0×@#@10-5Pa.Then,thedepositionwascarriedoutunderAratmospherewithabout2Paandthegasflowrateof18sccm.Duringthedepositionprocess,thecontinuousfilmofCowasalsodepositedontoaglasssubstrateunderthesameconditionfortheconvenienceofmeasuringthefilmthickness.@#@Thesurfacemorphologyoftheantidotarrayswasinvestigatedbythescanningelectronmicroscopy（SEM,JEOL2000）.Thegrazingincidencex-raydiffraction（GIXRD）,whichavoidstheeffectofsubstratetothepattern,wasusedtostudythecrystallinestructureofthefilm.Themagneticpropertiesinthetemperaturerange5K--300Kweremeasuredbyaquantumdesignmagnetometer（MPMSXLSQUID）.@#@Figure1showstheSEMpictureoftheCoantidotarraywithathicknessof15nm.Theantidotshaveawiderdiameterdistribution,whichthemeandiameterisapproximately150nm.Themeandistancebetweentheantidotcentresisabout250nm,whichindicatesthatthemeanconnectionsbetweentheantidotsareabout100nmwide.@#@Figure2showstheGIXRDpatternofthesample.Itshowsthatthefilmwithantidotarraysisapolycrystallinehexagonalclosed-packed（hcp）structure.Furtheranalysisshowsthatthecrystallitesizedistributesintherangeof5--10nm,calculatedwiththeScherrerformula.@#@Magnetichysteresisloopandtheinitialmagnetizationcurveat5KofthesampleareshowninFig.3,withthemagneticfieldparalleltothefilmplane.Theinitialmagnetizationcurveshowsthatthefieldrequiredtosaturatethematerialisintheorderofthesaturationloopcoercivefield,whichindicatesapinning-typecurve.[11]Thecoercivityofabout1300OeismuchlargerthanthatoftheCofilmonothersubstrates.[12]However,thesquarenessissmallerthanthatofothersubstrates.Thedifferenceofcoercivityandsquarenessbetweenantidotarrayandothercontinuousfilmmaybeduetothepinningoftheantidot.@#@ThecoercivityversustemperatureofCoantidotarrayfilmisshowninFig.4.Asthetemperaturedecreases,thecoercivityincreasesfirstly,attainsamaximumat50K,thendecreasesandreachesaminimumat5K.Thisanomalous