Ferromagnetic Coupling Field Reduction in CoFeB Tunnel Junctions Deposited by Ion Beam.

In this paper, junctions with reduced Hf coupling were fabricated by ion beam deposition and oxidation, using CoFeB electrodes. The CoFeB layer has a strong (111) texture that can be the origin of lower Hf and coercivity when compared, with CoFe. Junctions processed down to 2 × 4 μm² with 40-Å-thick CoFeB bottom electrodes have 42% of tunneling magnetoresistance (TMR), (R × A ∼ 400 Ω·μm²), Hc of ∼10 Oe and Hf of ∼2 Oe. CoFe-based junctions (R × A ∼ 500 Ω·μm²) have lower TMR (∼35%) and larger Hf (∼5-6 Oe) and Hc (∼12-14 Oe). Local chemical. composition analysis of the cross section indicated Fe-O segregation with very little Co grown on top of the barrier for CoFe-based junctions and not for CoFeB ones. [ABSTRACT FROM AUTHOR]