Intrinsic thermal robustness of tunneling spin polarization in Al/Al2O3/Co junctions

Abstract

Through a direct observation, based on the spin-polarized tunneling technique, we explore the thermal stability of tunneling spin polarization in Al/Al2O3/Co junctions. Thermal robustness of this parameter, which is of key importance for magnetic tunnel junction performance, is established for in situ postdeposition anneal temperatures up to 500 °C. This stability is consistent with detailed in situ x-ray photoelectron spectroscopy measurements on the Al2O3/Co system which show no structural changes during the anneal. Our results imply that, for comparable magnetic tunnel junction devices, thermal stability is not limited by intrinsic processes in the Al2O3 barrier and its interfaces. With ex situ postdeposition annealing in an Ar-atmosphere, which leads to severe degradation of the spin polarization above 250 °C, we demonstrate that the spin polarization is extremely vulnerable to diffusion of impurities.

X-Ray Absorption and Magnetic Circular Dichroism Studies of Co$_{2}$ FeAl in Magnetic Tunnel Junctions

“…This is in contrast to other studies were the Mn diffusion of the Mn-Ir towards the upper barrier interface was thought to be responsible for the decrease of the TMR ratio beyond 400°C [15]. On the other hand, a similar behavior was reported by Kant et al and Palusker et al [16][17][18]. Fig.…”

Spin Tunneling in Junctions with Disordered Ferromagnets

“…The high temperature anneal stipulates a crucial requirement for our junctions; viz., the barrier properties should not change after annealing to ensure comparison between the TSP of as-deposited and annealed CoFeB. Contrary to alternative barriers like MgO, AlO x barriers are known to exhibit no TSP related changes after anneals up to T a 500 C [12,13]. When the structure of Co 72 Fe 20 B 8 is intentionally transformed from amorphous to highly textured fcc, we notice that a correlated alteration of the CoFeB electronic structure is induced.…”

Thermal stability of tunneling spin polarization

“…The thermal stability is consistent with our earlier detailed in situ X-ray photo-electron spectroscopy (XPS) investigations of the AlO x /Co system. In this investigation no oxidation of Co at the interface, significant changes in the oxygen-Al ratio, or a shift of the oxygen-binding energies could be detected [9].…”