We have investigated a tunnel magnetoresistance (TMR) ratio of CoFeB/MgO perpendicular magnetic tunnel junctions (p-MTJs) with a 40 nm diameter as a function of an annealing temperature T a. The TMR ratio at room temperature (RT) increases with increasing T a and reaches 149 at T a = 350 °C, and further increase of T a results in a strong reduction of the TMR ratio, i.e., 2 at T a = 400 °C. The temperature dependence of the junction resistance versus magnetic field loops reveals that the reduced TMR ratio at RT is due to the disappearance of a stable antiparallel magnetization configuration. We find that reduction of dipole coupling restores the TMR ratio.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)