High-entropy bulk metallic glasses as promising magnetic ref

high-entropy alloy

JOURNALOFAPPLIEDPHYSICS117,073902

(2015)

High-entropybulkmetallicglassesaspromisingmagneticrefrigerants

JuntaoHuo,1,2LishanHuo,1,2JiaweiLi,1,2HeMen,1,2XinminWang,1,2AkihisaInoue,1,2,3ChuntaoChang,1,2,a)Jun-QiangWang,1,2,a)andRun-WeiLi1,2

KeyLaboratoryofMagneticMaterialsandDevices,NingboInstituteofMaterialsTechnology&Engineering,ChineseAcademyofSciences,Ningbo,Zhejiang315201,China2

ZhejiangProvinceKeyLaboratoryofMagneticMaterialsandApplicationTechnology,NingboInstituteofMaterialsTechnology&Engineering,ChineseAcademyofSciences,Ningbo,Zhejiang315201,China3

InternationalInstituteofGreenMaterials,JosaiInternationalUniversity,Tougane283-8555,Japan

1

(Received11December2014;accepted5February2015;publishedonline17February2015)Inthispaper,theHo20Er20Co20Al20RE20(RE¼Gd,Dy,andTm)high-entropybulkmetallicglasses(HE-BMGs)withgoodmagnetocaloricpropertiesarefabricatedsuccessfully.TheHE-BMGsexhibitasecond-ordermagneticphasetransition.Thepeakofmagneticentropychange

À1

KÀ1and627JkgÀ1at5T,respectively,(DSpkM)andrefrigerantcapacity(RC)reaches15.0Jkg

whichislargerthanmostrareearthbasedBMGs.Theheterogeneousnatureofglassesalsocontrib-pk

utestothelargeDSpkMandRC.Inaddition,themagneticorderingtemperature,DSMandRCcanbewidelytunedbyalloyingdifferentrareearthelements.TheseresultssuggestthattheHE-BMGsare

C2015AIPPublishingLLC.promisingmagneticrefrigerantatlowtemperatures.V

[http://www.77cn.com.cn/10.1063/1.4908286]

I.INTRODUCTION

Comparedwithconventionalgasrefrigerants,themag-neticrefrigerantsbasedonthemagnetocaloriceffect(MCE)haveadvantagesofbothhighef ciencyandenvironmentalfriendliness,demonstratingtheirpromisingfuture.1–4Themagnetocaloriceffectcanbecharacterizedbythe eldinducedentropychange(DSM)duetothealignmentofitsmagneticspinsthatoccursonexposuretoanexternalmag-netic eld.5Inthepastdecades,extensiveeffortshavebeencarriedoutinexploringthematerialswithexcellentMCE,1–17andsomematerialswithlargeDSMhavebeenfab-ricated,suchasMn-Fe-P-As,3Ni-Mn-In-(Co),4Gd5Si2Ge2,6LaFe11.4Si1.6,7andLa0.7Ca0.3MnO3.8Accordingtothemag-netictransitionstyle,themagneticrefrigerantscanbedi-videdintotwoclasses,the rstordermagneto-structuralphasetransitionmaterials(FOMTM)andsecondordermag-neticphasetransitionmaterials(SOMTM).2,9ForFOMTM,e.g.,Gd5Si2Ge2,themagnetizationshowsanabruptvariationatmagneticorderingtemperatureTC,leadingtoaverynar-rowandlargepeakofisothermalmagneticentropychange(DSpkM).However,thethermalandmagnetichysteresisoftheFOMTMmakesthemnotsuitablefortheapplicationofmag-neticrefrigeration.6TheSOMTMwithgradualandcontinu-ousmagnetizationvariationnearTC,exhibitingbroaderDSMpeaksandabsenceofthermalandmagnetichysteresis,arecurrentlyconsideredtobetheoptimalchoiceasthemagneticrefrigerants.9

AstheSOMTM,theglassymaterials,especiallytherareearth(RE)basedbulkmetallicglasses(BMGs)havecausedwideinterestsrecently.10–17Comparedtothecrystallinealloys,RE-basedBMGsmanifestlargeMCEoveramuchwidertemperaturerangeowingtotheiruniqueproperties

a)

associatedwiththeintrinsicamorphousnature,associatedwiththeirintrinsicnature,suchasthehigherelectricalresis-tivityandthusthesmallereddycurrentheating,highcorro-sionresistance,outstandingmechanicalproperties,andhighthermallystability,whichcausesthemtobesuitablecandi-datesformagneticrefrigerants.15Butuptonow,veryfewalloyswithlargeDSMandrefrigerantcapacity(RC)havebeenfabricated.ExploringnewBMGswithlargeDSMandRCisparticularlyimportanttoimprovetheef ciencyofrefrigerant.

Inthiswork,wedesignaseriesofhigh-entropybulkmetallicglasses(HE-BMGs)basedonthetraditionalRE-basedBMGsthathavelargeMCE.Differentfromthecon-ventionalBMGsthatareusuallycomposedofoneortwomajorelements,theHE-BMGsarecomposedofseveralele-mentswithequalconcentration.TheHE-BMGspossessingbothstrongtopologicalandchemicaldisorderhaveshownsomeuniqueandremarkablyimprovedproperties,com-paredwiththenormalBMGsandHEAs.18,19Theeffectofcomponent,temperature,andmagnetic eldonthemag-netictransitiontemperature,magneticentropychange,andrefrigerantcapacityisinvestigated.ThepresentHE-BMGsshowlargeDSM,widerDSMpeak,andthuslargerRC,com-paredtopreviousRE-basedBMGs.ItisdemonstratedthattheHE-BMGsarepotentialcandidatesformagneticrefrig-erantsworkinginheliumandhydrogenliquefactiontem-peraturerange.

II.EXPERIMENTALDETAILS

Authorstowhomcorrespondenceshouldbeaddressed.Electronicaddresses:ctchang@http://www.77cn.com.cnandjqwang@http://www.77cn.com.cn.Tel.:þ86-574-87617212.Fax:þ86-574-87617212.

ThealloyingotswithnominalcompositionsHo20Er20Co20Al20RE20(RE¼Gd,Dy,andTm)werepre-paredbyarcmeltingpureGd,Dy,Ho,Er,Tm,Co,andAl(>99.9wt.%)inaTi-getteredargonatmosphere.Then,theingotswereremeltedandsuck-castintoaCumoldtopreparethecylindricalrodswithadiameterof1mm.Theamorphous

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0021-8979/2015/117(7)/073902/5/$30.00117,073902-1

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