Effect of thickness of MgO, Co-Fe-B, and Ta layers on perpendicular magnetic anisotropy of [Ta/Co60Fe20B20/MgO]5 multilayered films

This study elucidates the magnetic properties of [Ta/Co60Fe20B20/MgO]5 as functions of thickness of each layer. Its perpendicular magnetic anisotropy (PMA) is found to depend strongly on the thickness of the MgO (tMgO) and Co-Fe-B (tCoFeB) layers. The Ta/CoFeB interface is critical to inducing PMA. A maximum room-temperature (RT) anisotropic energy (KuRT) of about 1 × 106 erg/cm3 and an anisotropic field (HkRT) of 4.7 kOe are obtained in the RT-prepared multilayered sample with tMgO = 1.0, tCoFeB = 1.3, and thickness of layer tTa = 10 nm. These values are comparable to the published values for Co60Fe20B20 after optimized field annealing. In this investigation, post-annealing has a more complicated effect on PMA in a multilayered structure than in a single or a double Co-Fe-B layer, both of which structure have been examined elsewhere. This result may be explained by the competing effects of the thermal process, which is an improvement of the crystallinity of Co-Fe-B and roughening of the interface.