Enhancement of coercivity by underlayer control in Co/Pd and Co/Pt multilayers

Co/Pd and Co/Pt multilayers were sputtered on Pd or Pt underlayers and the effects of sputtering pressure during the formation of underlayers on the magnetic properties of multilayers were investigated. It was found that the coercivity of Co/Pd multilayers was strongly dependent on the sputtering pressure of underlayer and could be increased drastically from 1.2 kOe up to around 5 kOe merely by increasing the sputtering pressure of Pd underlayer from 6 mTorr to 24 mTorr, while in case of Co/Pt films, no significant change of the coercivity could be observed with the variation of sputtering pressure of the underlayer. For both multilayers, the magnetic reversal feature was affected by the surface roughness of the underlayer and multilayers grown on the underlayer with a rough surface favored a rotation dominated process. The Kerr rotation angle was found to be hardly affected by the preparation conditions of the underlayer.