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The magnetic and interface properties of [Pt/Co/Pt] were investigated. First, the magnetic properties were determined from the magnetic dead layer plots, in which the Co layer was considered as two distinct parts representing different magnetic properties. The two parts with low and high tCo ranges are close to and away from the top interface (Co/Pt), respectively. The part close to the top interface shows a smaller magnetization (M) value and nonlinear behavior. However, the other part shows a higher M value closer to the bulk value and a linear behavior. The nonlinear behavior of the M values of the low tCo range was converted to an impurity level using simple assumptions. The results showed the effect of the top Pt layer on the magnetic properties of the Co layer. The results clearly demonstrate that magnetometry could be utilized as a means to understand the interface quality of magnetic multilayer systems.

The perpendicular magnetic anisotropy (PMA) and crystalline structure of Ta/NiFeB/MgO stacks are investigated. When the stack is annealed, PMA is induced and the magnetic moment increases due to the crystallization of bcc NiFe from amorphous NiFeB. This structure is combined with [Pt/Co]6 multilayers to study the change in the magnetic coupling and PMA behavior with the change in the Ta thickness inserted in-between and the annealing temperature. Among the [Pt/Co]6/Ta/NiFeB/MgO stacks, the stack with a 0.5-nm-thick Ta layer shows the strongest PMA with an effective PMA energy density of 4.4 × 106 erg/cm3 upon annealing at 400 °C. Further, the X-ray diffraction study of the crystalline structures confirms the formation of the NiFe (001) phase, which is essential for achieving a high tunneling magnetoresistance ratio.

The effects of inserting an amorphous FeZr layer between the [Pt/Co] multilayer and the CoFeB/MgO layer in stacks possessing perpendicular magnetic anisotropy are examined. A 1-nm-thick FeZr layer is effective in forming a bcc (001)-textured CoFe layer during annealing by suppression of crystallization at the interface with the multilayer, which is terminated in a close-packed plane. Because FeZr is magnetic, it has an advantage over Ta, an alternative material used for the same purpose. Efficient magnetic coupling between the multilayer and CoFeB/MgO occurs even for large FeZr layer thicknesses, so the magnetic properties of the stack are only weakly affected.