Spin Tunneling in Junctions with Disordered Ferromagnets

Abstract

Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. We provide compelling evidence to establish that, contrary to one's elementary guess, the tunneling spin polarization (TSP) of amorphous CoFeB is larger than that of fcc CoFeB. First-principles atomic and electronic structure calculations reveal striking agreement between the measured TSP and the predicted s-electron spin polarization. Given the disordered structure of the ternary alloy, not only do these results strongly endorse our communal understanding of tunneling through AlO x , but they also portray the key concepts that demand primary consideration in such complex systems.

Magnetism in Co80-xFexB20: Effect of crystallization

“…2(a). However, crystallization alone cannot explain the sharp and large change in coercivity that is observed around t ¼ 22 nm, because it is known that layers thinner than 22 nm also crystallize after annealing at T a ¼ 450 C. 12,13,19 These observations show that the effect of the crystallization on the magnetic properties of Co 60 Fe 20 B 20 is thickness dependent, suggesting that the local morphology of the layer may have a large effect on the coercivity. A key parameter, then, would be the size of the crystallized grains.…”

“…In Region 2, at the transition, a combination of a square and a rounded loop is seen, indicating that both reversal mechanisms are present at the transition region. Based on previous studies, 12,13,19 it is known that annealing the as-deposited sample crystallizes the CoFeB, which explains the overall increase in coercivity that is observed in Fig. 2(a).…”

“…1, the XRD intensity pattern for as-deposited and annealed (T a ¼ 450 C) samples is shown for the region of interest, where diffraction peaks are known to appear for crystallized Co 80Àx Fe x B 20 . [16][17][18][19] We have chosen to limit our XRD analysis to relatively thick films of t ¼ 70 nm to obtain a sufficient signal to noise ratio. In the as-deposited case, as expected for an amorphous film, we do not observe any diffraction peaks other than from the Si substrate over a large range of diffraction angles (a representative measurement for x ¼ 80 is shown).…”

Structural and magnetic changes in MgO-based magnetic tunneling junctions during the early stages of annealing

“…The large rise in R AP , and concomitant high TMR ratio, are consistent with this, and we can conclude that the appropriate bcc phase of CoFe is starting to form. The D 1 coherent tunneling is essential to the rise in TMR, as CoFeB has a markedly lower TSP in crystalline form [37], which would give rise to a drop in TMR if this transport channel were not present. It is noteworthy that at the higher values of Q z the changes in the SA at the Fe edges are more pronounced than those at the Co edges.…”

Teoria do momento angular em sistemas complexos

“…Neste contexto, é intuitivo esperar que duas cadeias de spin com magnetizações distintas, ou diferentes níveis de ordem, entrem em equilíbrio caso possam interagir com um meio em comum, que passa a desempenhar um papel de mediador de excitações, acoplando as cadeias [166]. Essa transmissão pode ser interpretada como tunelamento de spins entre cadeias ou como uma corrente de spins [167][168][169].…”