Effects of an ultrathin MgO inserted layer on the magnetic properties of FePt films

Face-centered-tetragonal L1(0) Fe/Pt multilayers have been prepared by molecular-beam epitaxy on MgO (001) substrates at 500 degrees C. An ultrathin MgO layer, 1, 3, and 5 nm in thickness, respectively, was inserted into the middle of Fe/Pt multilayers by using an e-beam evaporation without introducing any oxygen source. The insertion of MgO layer effectively reduced the average grain size and the size of magnetic domains. Out-of-plane coercivity of the FePt films decreased with increasing thickness of the MgO insert layer. It was found through the studies of angular dependent coercivity that upon MgO insertion the decrease in coercivity is originated from the weakening of domain-wall motion, while domain rotation is enhanced depicting a decoupling of intergrain interaction. (c) 2005 American Institute of Physics.