Evolution of the interfacial magnetic anisotropy in MgO/CoFeB/Ta/Ru based multilayers as a function of annealing temperature

Abstract

We report the effect of annealing temperature on the dynamic and static magnetic properties of MgO/CoFeB/Ta/Ru multilayers. Angular resolved ferromagnetic resonance measurement results show that the as-deposited film exhibits in-plane magnetic anisotropy, whereas in the annealed films the magnetic easy-axis is almost along the direction perpendicular to the plane of the layers. The extracted interfacial anisotropy energy, Ki, is maximized at an annealing temperature 225∘C, in agreement with the vibrating sample magnetometry results. Although the magnetization is not fully out-of-plane, controlling the degree of the magnetization obliqueness may be advantageous for specific applications such as spin-transfer oscillators.

CoFeB/MgO/CoFeB structures with orthogonal easy axes: perpendicular anisotropy and damping

“…Although it is counter-intuitive that the thinner B layer possesses an in-plane easy axis, the same feature has been reported for other Ta/CoFeB(1 nm)/MgO systems deposited in the same TIMARIS equipment [17]. Similar effect has been recently observed in a substrate/MgO/CoFeB/Ta/CoFeB/ MgO structure, where the thicker CoFeB layer exhibits a strong PMA in contrast to the relatively weak PMA in the thinner CoFeB layer [18,19].…”

“…On the other hand, the linewidth ∆H strongly broadens to ∼ 400 Oe and ∼ 700 Oe for the B layer and the T layer, respectively. These values are in agreement with recently reported values for a similar systems [17]. Moreover, as it is shown in Fig.…”

“…Therefore, it is impossible to determine α precisely for the annealed systems. Such a behavior of ∆H and the decreased remanence with respect to the saturation magnetization (see, [17]) both confirm a strong angular dispersion of the easy PMA axis in both layers. It has been observed that with increasing PMA the dispersion of anisotropy also increases [6,7,27].…”

Ion irradiation-induced easy-cone anisotropy in double-MgO free layers for perpendicular magnetic tunnel junctions

“…Mn2RhSn (Ref. 10 )), multi-layers containing the FeCoB/MgO interface can also exhibit easy-cone anisotropy, when the FeCoB thickness is properly adjusted to be close to the reorientation from out-of-plane to in-plane anisotropy [14][15][16][17][18][19] .…”

“…One should notice that the easy-cone anisotropy can be useful not only for STT-MRAM but also for other spintronic applications such as spin-torque oscillators 22 and magnetic sensors 11,19 .…”