We have investigated magnetotransport properties of magnetic tunnel junctions (MTJ) with rock-salt type ZnO(001) or MgO/ZnO(001) barriers by both calculation and experiments. The first-principles transmission FDOFXODWLRQV EDVHG RQ 1(*) PHWKRG FODULIHG WKDW WKH 0J2=Q2 EDUULHU KDG FRKHUHQW WXQQHOLQJ WKURXJK Ʀ1 state such as a conventional MgO(001) barrier. Experimental results revealed that the MTJs with an MgO/ZnO barrier had an MR ratio of 70 % at a low resistance-area(RA) product of 0.5 :Pm 2. This MR ratio is almost the same as the MgO barrier or higher. The rock-salt type ZnO(001)-based MTJs seem to be suitable for application to the read magnetic heads of hard-disk drives (HDDs) with an areal recording density of over 500 Gbits/in 2 .
Crystallographic orientation of the MgO barrier in sputter-deposited CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) and its effect on tunnel magnetoresistance (TMR) were investigated. The degree of MgO(001) orientation was estimated with the integral intensity ratio (I (200) /I (220)) of diffraction lines from MgO(200) and MgO(220) planes obtained in grazing incident x-ray diffraction profiles. The main results are stated as follows. (1) I (200) /I (220)~ 4, meaning the (001) orientation of MgO, is realized when the underlaid CoFeB maintains amorphous structure, meanwhile MgO on bcc(110)-oriented CoFe shows (111) orientation (I (200) /I (220) = 0). (2) The prevention of epitaxial growth on hcp(00.1)-oriented Ru layer is effective to maintain amorphous structure of CoFeB. (3) The achievable TMR ratio after high temperature (280 ºC 450 ºC) annealing is mainly dominated by the MgO orientation and giant TMR ratio exceeding 200% is only obtained with I (200) /I (220) 3.4, while the resistance area product is independent of I (200) /I (220). (4) Thin Mg layer inserted between CoFeB layer and MgO barrier is effective to obtain bcc(001)-oriented crystallization of CoFeB after high temperature annealing and results in a giant TMR ratio, because of its role to avoid surface oxidization of underlying ferromagnetic electrode during the deposition of MgO barrier.
α′ and γ′-Fe-N with various N contents were synthesized by using multilayer fabrication technique and the volume effect on magnetic moment for these phases was examined. The unit-cell volume of α′ and γ′ phases monotonously increases with increasing N content. In the case of α′-Fe-N, magnetic moment decreases with increasing unit-cell volume. This result is different from theoretical prediction. On the other hand, in the case of γ′-Fe-N, magnetic moment takes the maximum near the volume of bulk γ′-Fe4N. In particular, the magnetic moment drops drastically near the volume of bulk γ′-Fe4N, although unit-cell volume is almost same. This result is also different from the theory. Further experimental works including magnetic microstructural analysis are needed to answer these discrepancies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.