CoFeB Thickness Dependence of Thermal Stability Factor in CoFeB/MgO   Perpendicular Magnetic Tunnel Junctions
  Thermal stability factor (delta) of recording layer was studied in perpendicular anisotropy CoFeB/MgO magnetic tunnel junctions (p-MTJs) with various CoFeB recording layer thicknesses and junction sizes. In all series of p-MTJs with different thicknesses, delta is virtually independent of the junction sizes of 48-81 nm in diameter. The values of delta increase linearly with increasing the recording layer thickness. The slope of the linear fit is explained well by a model based on nucleation type magnetization reversal. 
H. Sato, M. Yamanouchi, K. Miura, S. Ikeda, R. Koizumi, F. Matsukura   and H. Ohno
cond-mat.mtrl-sci