I nhau c6 cau hinh AP Di/di tac dung cua iii tnidng ngoai, cau hinh AP se chuyen thinh cau hinh P Khi d6, iH do cua tat c^ cac dp deu song song vdi iil tri/dng
64 Nguyin Hiiu Diifc
Mot Uu di^m khac cua cac vat lieu nfe kim loai la cd th^ dUdc SLf dung vdi
chiifc nang ghi nhan spin (spin detection hay spin analyzer) vh xac dinh dau cua
sU phan cUc spin trong cac he TMR kieu FM/IS/HM. ThUe vaỵ neu sU phan cUc spin trong HM da biet trUde (P = ± 1), dUa vao dang cua hieu ifng TMR ta se xac
dinh dxiac dau eua sU phan cUe spin trong cUe FM. Cu the lạ neu sU phan cUc spin trong hai cUc FM va HM la nhu nhau, hieu ling TMR thuang se dUdc quan
sat: RAP > Rp va TMR ed gia tri dUdng. NgUde lai, neu sU phan cUe spin d trong
hai dien cUc ngUde nhau, hiiu ung TMR nguac se duac quan sat: R^p < Rp v^ TMR cd gia trj am. Mot sd ket quh nghien cifu sU phan cUc spin b^ng each n^y eua nhdm Gs. Ạ Pert (CNRS -Thales, Phap) duac gidi thieu dUdi day (hinh 6a-d).
100 •50 0 50 100
Bo (mT)
Hinh 5. Diarng cong TMR ciia LSMOISTOILSMO
LSMO la vat lieu ntfa kim loai vdi sU phan cUc spin dUdng, da dxiac suf dung
de nghien cuH trong he Co/IS/LSMỌ vdi IS = SrTiOa (STO), Ce,.,La,025 (CLO), AI2O3 (ALO) hoac ALO/STỌ Trong trUdng hdp hang rao la ALO, hieu ifng TMR
thong thudng da dxicjc quan sat (hinh 6a), tUdng ifng vdi sU phan cUe spin dUdng
eua Cọ Khi suf dung hang rao la STO hoac CLO, hieu iifng TMR ngUde xSy ra
(hinh 6b,e). Dieu nay chifng to spin Co c6 sU phan cUc am, tifc la phan cxic spin
eua cac kim loai cd the thay đi tuy thupc vao ban chat eua viing be mat tiép xuc. Hdn the nifa, sU khac nhau ay cdn lien quan den phan ttf tai dien trong Idp dien moị Trong Idp ALO, cac phan tif tai dien la cac dien ttf s ed phan cUc spin dUdng, cdn trong STO va CLO, cac dien tif d ed spin phan cUc am tham gia vao
sU tai dien. Neu stf dung hang rao kep (double barrier) ALO/STO, hieu ifng TMR nhan dx.iac tUdng tU nhU trUdng hdp hang rao ALO (hinh 6d); chifng td vai trd chu
Spintronics dUa tren hieu Ung tit - dien tr6... 55 y^u cua viing tiefp xuc FM/IS. Cac ket qui nghien cifu viec ghi nhan spin dang phat triin manh, cho phep khong nhCfng hieu biet dUdc ed che vat ly cua qua trinh TMR ma cdn de che tao cac linh kien cd tiieu suat caọ
Co/ALO/LSMO Co/STO/LSMO •ISO -100 TCr trudng (mT) Co/CLO/LSMO Til trudng (mT) Co/ALO/STO/LSMO .20 0 20 Tir trudng (mT) -2S 0 2S TU trudng (mT)
Hinh 6. Duong cong TMR ciia cdc he ColllLSMO vdi / = AljOj (a), SrTiOj (b), Ce-La-0 {c)vaAipjSrTiOi{d)