Local transport properties of Co-Fe/Al-O/Co-Fe tunnel junctions with high thermal stability

• Published in: Journal of magnetism and magnetic materials Vol. 284; pp. 330 - 335
• Main Authors: TAE SICK YOON, SHOYAMA, Toshihiro, YOUNG WOO LEE, TSUNODA, Masakiyo, TAKAHASHI, Migaku, DONG YOUNG KIM, CHONG OH KIM
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Science 01.12.2004
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electronic transport in condensed matter; Exact sciences and technology; Physics; Spin polarized transport; Fowler-Nordheim theory; Annealing; Fowler-Nordheim equation; 75.70 cn; Ferromagnetic materials; Thermal stability; Thickness; Multilayers; Temperature effects; Tunnelling magnetoresistance; 75.70 pa Tunnel magnetoresistance; Local transport properties; Tunnel junction; Transport processes; Barrier height
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2004.07.032

In order to investigate the annealing temperature dependence of the tunnel magnetoresistance ratio (TMR) for ferromagnetic tunnel junction, the local transport properties were measured for Ta 5 nm/Cu 20 nm/Ta 5 nm/Ni76Fe24 2nm/Cu 5nm/Mn75Ir25 10nm/Co71Fe29 4nm/Al-O junction with metal Al thickness of 0.8 nm and oxidization time of 7s. The current histogram statistically calculated from the electrical current image was in good accordance with the fitting result considering the Gaussian distribution of barrier height and Fowler-Nordheim conductance. At high annealing temperature of 340DGC, where the TMR ratio of the corresponding MTJ had the maximum value of 44%, the average barrier height phiave increased to 1.12 eV and the standard deviation sigmaphi decreased to 0.1 eV. The increase of TMR ratio after annealing was attributed to the increase of average barrier height and decrease of the barrier height variation. After further annealing at 360 deg C, the standard deviation sigma, increased up to 0.2 eV and the TMR decreased to 10%.