Coupling strength with off-axial external field in magnetic tunnel junction cells

摘要

A series of hysteresis loops with off-axial external magnetic fields have been measured to identify magnetization reversal properties as well as coupling effects in magnetic tunnel junctions (MTJs). MTJ films, consisting of a synthetic artificial antiferromagnetic pinned layer of CoFeB/Ru/CoFe/ IrMn, were patterned into an elliptical cell array with sizes of 200×300 nm and 500×750 nm. The hysteresis loops were measured using a vibrating sample magnetometer with various directions of the external magnetic field; the angle θ between the external magnetic field (He) and the biasing field of the pinned layer (H_B) was varied from 0° to 90°. The two significant coupling effects, ascribed to exchange bias between CoFe/IrMn and Ruderman-Kittel-Kasuya-Yosida-like coupling in CoFeB/Ru/CoFe, can be observed in these hysteresis loops. The angular dependence of the hysteresis loops is employed to characterize the variation of these coupling effects in extended and patterned MTJ films.