Ferromagnetic coupling field reduction in CoFeB tunnel junctions deposited by ion beam

In this paper, junctions with reduced H-f 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 H-f and coercivity when compared with CoFe. Junctions processed down to 2 x 4 mum(2) with 40-Angstrom-thick CoFeB bottom electrodes have 42% of tunneling magnetoresistance (TMR), (R x A similar to 400 Omega.mum(2)), H-c of similar to10 Oe and Hf of similar to2 Oe. CoFe-based junctions (R x A - 500 Omega.mum(2)) have lower TMR (similar to35%) and larger H-f (similar to5-6 Oe) and H-c (similar to12-14 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.