非均勻系統(tǒng)磁輸運(yùn)性質(zhì)的研究.pdf

1、蘇州大學(xué)碩士學(xué)位論文非均勻系統(tǒng)磁輸運(yùn)性質(zhì)的研究姓名：鞠艷申請學(xué)位級別：碩士專業(yè)：凝聚態(tài)物理指導(dǎo)教師：李振亞2001.5.1ABSTRACTThediscoveryofgiantmagnetoresistanceeffecthasattractedmuchattentiontesearchofmagnetictransportininhomogeneoussystems，whichdependsOilspinofelectronsThem

2、agnetoresistanceinsuchtwoinhomogeneoussystemsasmagneticgranularalloysanddopedpervoskitemangauitefilmsisusuallyconsideredduetospin。dependentscatteringAppfiedmagneticfield，thesymmetricbrokenbetweenspin‘upandspin—downchanne

3、lsgivesrisetothegreatdecrementofresistanceTherearemainlytwowaysoftheoreticstudyonGMRinmagneticgranularalloysOneistoextendedthequantumOIquasi—classicaltreatmentsofGMRinmultilayerstotheoneinmagneticgranularsystemsTheotheri

4、saphenomenologicalmethodwhichadopeseffectivemediumapproxiation(EMA)andtwochannelmodeldirectlyWithintheframeworkofthelatterone，theGMRdependenceontemperatureandvolume—fractionisdiscussedinthepaper，withconsiderationofdiffer

5、entkindsofmagneticentitiesEMA，assumesthecomponentsdistributedinhighlyrandomfashion，isausefulmethodtotreatthetransportpropertiesofgranularcomposites，andtheeffectiveconductanceofcompositescouldtobederivedsdfconsistentlybys

6、ubstitut—ingtheactualenviromentofthestudiedgrainwitheffectivemediumNevertheless，itseemstobequiteunsatisfactoryforinvlestigationtheeffectivepropertiesofsystemsduetoignoringtherealisticstructuresofthemediumActually，formerr

7、eseaschesdemenstratethatbothtinyclustersformedbyseveralmagneticatomsandbigclustersformedbymagneticgrainse】dstinml：nsbesidesisolatedgrainsInthepaper，wetaketheeffectoftinyclustersintoaccuntandfindthattheratiooftinyclusters

8、tograinschangeindifferentsamplesThecalculatedresultsareingoodagreementwithexperimentaldatafortemperaturedependenceTakingtheeffectofbigcluitersintoaccount，weexplainthevolume—fractiondependencequalitativelybyeffectiveOuste