The measurement of force per width of CoCrX/Cr (X=Pt,Ta) bilayer showed that both the surface state and surface stress of CoCrX layer can be controlled by controlling the surface stress of Cr underlayer through the variation of its thickness and of the deposition conditions such as the deposition rate and temperature. The dynamic surface of CoCrX layer showing a compressive surface stress was a critical factor to determine its coercivity. This was because the phase decomposition of CoCrX alloy can be largely promoted at the compressive dynamic surface because of its high mobility. (c) 2005 American Institute of Physics.