A series of Co/Pt974Mn26(xPtMn nm)modulated multilayers with the thickness of PtMn layer x ranging from 096 to 168nm have been prepared by a magnetron sputtering system on 40nm thick PtMn buffer.With combined small-and large-angle x-ray analyses,the layered and crystal structure of the samples were investigated.Magnetic hysteresis loops and perpendicular magnetic anisotropy(PMA) were obtained by means of altermating-gradient magnetometer(AGM) and magnetic torque methods.Saturation magnetization,PMA and the Kerr spectrum of the samples were also investigated.Through analyses,we obtained the variation of Kerr rotation with the increase of PtMn thickness,which was ascribed to the reduction of the polarization of Pt atom and the interlayer alloys.