Observation of uniaxial magnetic anisotropy and out-of-plane coercivity in W/Co20Fe60B20/W structures with high thermal stability

In this study, the development of uniaxial magnetic anisotropy (UMA) and out-of-plane coercivity (H-c(perpendicular to)) in W/Co20Fe60B20 (CoFeB)/W structures by tuning the annealing temperature (T-A) such as 300 degrees C, 400 degrees C and 500 degrees C were achieved. For 400 degrees C film, W and CoFeB interfaces play a major role in achieving the large H-c(perpendicular to). Furthermore, the observation of large H-c(perpendicular to) was found to be significantly induced by the interface on the two sides of CoFeB layer. The two-fold UMA strongly is stabilized in W/CoFeB/W trilayers up to 500 degrees C. A maximum in-plane uniaxial anisotropy energy density (K-u) was observed for the 500 degrees C annealed films, which is accompanied by the dominance of H-c(perpendicular to) owing to the over-oxidation and/or occurrence of inter-diffusion across the interfaces. The oxidation and relieving of boron atoms in the CoFeB at higher annealing temperatures were confirmed by X-ray photoelectron spectroscopy (XPS). The control over the interface shared between the W and CoFeB is concluded to be essential in order to alter the strength of magnetic anisotropy. Hence, an investigation on W/CoFeB/W structures could be very beneficial for the modern Spin-Orbit Torque (SOT) based data storage applications and this inspires relevant research work to widen magnetic systems. (C) 2021 Elsevier B.V. All rights reserved.