3485

3291

كارشناسي ارشد

فيزيك

اصفهان: دانشگاه صنعتي اصفهان، دانشكده فيزيك

1385

[يازده]، 105، [II] ص.: مصور، جدول، نمودار

ص. ع. به فارسي و انگليسي

هادي اكبرزاده

پرويز كاملي

26/2/86

سعيد جلالي اسدآبادي

اكبر جعفري

1396/02/25

كتابنامه

فيزيك

فيزيك

ID3291

به فارسي و انگليسي: قابل رويت در نسخه ديجيتال

AbstractOne of the main challenges in the eld of spintronic is the spin injection from a metal into a semicon ductor Currently the half metallic ferromagnetic Heusler alloys are at the focus of a large scienti cinterest due to their potential for maximizing the e ciency of spin polarized current As predictedby rst principle calculations in these compounds one spin direction behaves like a metal whereas for the other spin channel the fermi level is located is a gap Thus their Fermi spin polarization isP 100 However the half metallicity can be lost in the vicinity of boundary with semiconductorsdue to interfaces states which arise from disordering or atomic intermixing So it is crucial to studythe junctions between a half metal and a semiconductor focusing in particular on the interface related e ects on the relevant electronic and magnetic properties Co Cr F e Al is one of theFull Heusler alloys that has been shown to possess half metallic electronic structure with a high Curietemperature Tc 665 and a large magnetoresistance 37 in a small magnetic eld of about0 25T To our knowledge theoretical work on Co Cr Fe Al s interface with semiconductors sub strate has not been performed yet So it is not clear whether it keeps high spin polarization at itsinterface or not This motivated us to investigate the interface of this system with GaAs substratewhich is one of the well known semiconductors in electronic technology In this thesis using theESPRESSO code we rst studied the bulk properties of Co Cr Fe Al This alloy has a simillarstruture with Co Cr Fe Al while it needs a smaller supercell our bulk results have shown thatCo Cr Fe Al heusler alloy is a half metal Then we studied the electric and magnetic propertiesof Co Cr Fe Al GaAs 001 interface All of our calculation are within the framework of densityfunctional theory by using the plane wave pseudopotential approach Our results for the variousinterfaces show that half metallicity is destroyed for all interfaces possibilities A noticable point isthat a high degree of spin polarization is obtained at CrAl As termination 78 which is the moststable interface Furthermore our calculation shows that in such heterostructure modifcation with apure Cr cap considerably increase the spin polarization due to the strong surface subsurface coupling Finally the band alignments and shottky barrier were extracted for the majority and minority spinchannels

هادي اكبرزاده

پرويز كاملي