Tunnel Magnetoresistance above 170% and Resistance–Area Product of 1 Ω (µm)2 Attained by In situ Annealing of Ultra-Thin MgO Tunnel Barrier

CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) prepared by sputtering deposition and in situ annealing exhibited a high magnetoresistance (MR) ratio (above 170%) and an ultra-low resistance–area (RA) product [about 1.0 Ω (µm)2]. The MgO barrier, which was about 1 nm thick, was initially amorphous. In situ annealing of the barrier at 300 °C promoted crystallization of the MgO with (001) orientation, which resulted in the high MR ratio at the ultra-low RA product. The present achievements will enable the development of highly sensitive tunnel magnetoresistive (TMR) read heads for hard disk drives with a recording density of about 1 Tbit/in.2.