Reduction of electron tunneling current due to lateral variation of the wave function

Structural defects analysis versus spin polarized tunneling in Co2FeAl/MgO/CoFe magnetic tunnel junctions with thick MgO barriers

“…Related to the quenching of the crystal symmetry coherence across the MTJ stack, in these systems the coherence of the electronic Bloch functions in the single crystal CFA electrode is destroyed both along the propagation direction, by the oblique dislocation network within the thick barrier, and in the plane of the MTJ stack due to the large density of misfit dislocations. Moreover, this reduction of the lateral coherence of the wave function in single crystal MTJs is particularly detrimental to symmetry dependent filtering in single crystal MTJs, where the attenuation rate within the insulator depends on the in-plane modulation of the tunneling Bloch wave function [25]. Our analysis provides a reasonable effective spin polarization of 0.57 at OK for our CFA/MgO-thick system which confirms the absence of ∆ 1 band symmetry filtering within the thick MgO barrier.…”

Competing Anisotropy-Tunneling Correlation of the CoFeB/MgO Perpendicular Magnetic Tunnel Junction: An Electronic Approach

“…TMR, which is physically supported by the different tunneling possibilities for majority/minority electrons, is therefore expected to be reflected by XMCD. In other words, the XMCD intensity (i.e., spin polarization) of the d [001] would reveal TMR information because the spin-polarized d [001] state shares electronic similarities with the specific tunneling mechanism of CoFeB/MgO 2 3 7 . Following this principle, therefore, a higher TMR ratio should be achieved by increasing the CoFeB thickness, because of the enhanced spin polarization of the d [001] states, on the basis of the XMCD results.…”

“…Recent studies had revealed that the d -band filling of the CoFeB with less z -correlated characteristics would give rise to PMA 5 6 . From a transport standpoint, an electronic channel with z -correlation would favor spin tunneling across the junction, according to Bloch theory 7 . These independent studies imply that though PMA and TMR share common characteristics in the orbital symmetry, a competing relationship may exist between the two physical characteristics owing to their opposite preferences in electronic occupation.…”

Spintronics: Fundamentals and applications

“…With a few exceptions (Worledge and Geballe, 2000b), F/I/S conductance measurements (Tedrow and Meservey, 1994) have revealed positive P -the dominant contribution of majority spin electrons for different ferromagnetic films (for example, in Fe, Ni, Co and Gd). However, electronic structure calculations typically give that N F ↑ < N F ↓ and P N < 0 [for Ni and Co N F ↑ /N F ↓ ∼ 1/10 (Butler et al, 2001)].…”