Large planar Hall effect in perpendicularly magnetized W/CoFeB/MgO structures

• A large planar Hall effect is observed in W/CoFeB/MgO samples.
• We examine the variation of the planar Hall effect with different CoFeB thickness.
• The planar Hall effect is insensitive to the CoFeB thickness.
• The large planar Hall effect is attributed to the strong spin-orbit coupling of the W.

The planar Hall effect (PHE) in W/CoFeB/MgO structure with perpendicular magnetic anisotropy was investigated as a function of CoFeB thickness (tCoFeB). The PHE is measured by sweeping the in-plane magnetic field at various azimuthal angles as well as by rotating strong magnetic field which is enough to saturate the magnetization. We observed a huge PHE in the W/CoFeB/MgO sample, which is even larger than anomalous Hall effect (AHE). This is distinct from the results in Ta/CoFeB/MgO samples showing a much smaller PHE than AHE. Since the PHE is insensitive to the tCoFeB while the AHE is proportional to the tCoFeB, the unprecedented PHE can be attributed to the W layer with a large spin-orbit coupling.