Patterned nanoring magnetic tunnel junctions and current-induced magnetization switching

Patterned nanoring (NR) magnetic-tunnel-junctions (MTJs) with outer diameters between 100 and 400nm and narrow ring widths between 25 and 30nm were successfully fabricated. The NR structure consists of CoFeB electrodes and Al-oxide barrier. The tunnelling magnetoresistance (TMR) ratio of the patterned NR-MTJs is in the range of 20\%-50\% observed at room temperature with $RA$ lower than $50\Omega \mu$m$^2$. These NR- MTJs allow current-induced magnetization switching with a low switching current density of around $9\times 10^6 A /cm^2$. Due to the small stray field and high TMR ratio, NR-MTJs offer superior prospects for very high density magnetic random access memory (MRAM), recording medium and other spintronics devices.