Magnetic aftereffect and magnetic force microscopy studies of Fe-B/FePt-type nanocomposite ribbons

Magnetic aftereffect and surface magnetic domain structure of (Fe0.675Pt0.325)(100-x)B-x(x=12-20) nanocomposites have been investigated for correlating with their corresponding phases and magnetic properties. Exchange-coupling effect between grains is present for all the studied ribbons as evidenced by Henkel plot. The volume fraction of magnetically soft phases decreases with increasing B concentration from x=12 to x=18. It leads to the reduction in the activation volume of the reverse domain. Among all samples, the (Fe0.675Pt0.325)(82)B-18 ribbon having the highest intrinsic coercivity (H-i(c)) exhibits minimum value in activation volume V=1.1x10(-18) cm(3), because it possesses the least volume fraction of the magnetic soft phases, i.e., Fe2B or Fe3B phases. Magnetic force microscopy studies reveal the magnetic domain structures of the ribbons, confirming the existence of strong exchange coupling between magnetic grains. (C) 2006 American Institute of Physics.