MgO thickness-induced spin reorientation transition in Co_0.9Fe_0.1/MgO/Co_0.9Fe_0.1 structure

Highlights: • Magnetic anisotropy of the bottom Co_0.9Fe_0.1 layer of the Mo/Au/Co_0.9Fe_0.1/Au/MgO(t_MgO)/Au/Co_0.9Fe_0.1/Au structure depends on the MgO spacer thickness. • Upon variation of t_MgO, the uniaxial out-of-plane magnetic anisotropy undergoes a spin reorientation transition at t_MgO of about 0.8 nm. • An interlayer exchange coupling between Co_0.9Fe_0.1 layers through the thin MgO film was proposed as a possible mechanism of the origin of the observed spin reorientation transition. - Abstract: The magnetic anisotropy (MA) of Mo/Au/Co_0.9Fe_0.1/Au/MgO(0.7–3 nm)/Au/Co_0.9Fe_0.1/Au heterostructure has been investigated at room temperature as a function of MgO layer thickness (t_MgO). Our studies show that while the MA of the top layer does not change its character upon variation of t_MgO, the uniaxial out-of-plane MA of the bottom one undergoes a spin reorientation transition at t_MgO of about 0.8 nm, switching to the regime where the coexistence of in- and out-of-plane magnetization alignments is observed. The magnitudes of the magnetic anisotropy constants have been determined from ferromagnetic resonance and dc-magnetometry measurements. The origin of MA evolution has been attributed to a presence of an interlayer exchange coupling (IEC) between Co_0.9Fe_0.1 layers through the thin MgO film.