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

• Published in: IEEE transactions on magnetics Vol. 40; no. 4; pp. 2272 - 2274
• Main Authors: Cardoso, S., Ferreira, R., Freitas, P.P., MacKenzie, M., Chapman, J., Ventura, J.O., Sousa, J.B., Kreissig, U.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01-07-2004; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amorphous materials; Chemical analysis; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electrodes; Exact sciences and technology; Ion beams; Magnetic analysis; Magnetic films; Magnetic properties and materials; Magnetic tunneling; Magnetism; Optical coupling; Oxidation; Physics; Tunneling magnetoresistance; CoFeB electrodes; Magnetic materials; tunnel junctions; ion beam deposition; low ferromagnetic coupling
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2004.832147

In this paper, junctions with reduced H/sub 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/sub f/ and coercivity when compared with CoFe. Junctions processed down to 2/spl times/4 /spl mu/m/sup 2/ with 40-thick CoFeB bottom electrodes have 42% of tunneling magnetoresistance (TMR), (R/spl times/A/spl sim/400 /spl Omega/./spl mu/m/sup 2/), H/sub c/ of /spl sim/10 Oe and H/sub f/ of /spl sim/2 Oe. CoFe-based junctions (R/spl times/A/spl sim/500 /spl Omega/./spl mu/m/sup 2/) have lower TMR (/spl sim/35%) and larger H/sub f/ (/spl sim/5-6 Oe) and H/sub c/ (/spl sim/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.