Closely linear temperature dependence of exchange bias and coercivity in out-of-plane exchange-biased [Pt/Co]3/NiO(11 Å) multilayer

Strong out-of-plane exchange biasing has been observed in out-of-plane exchange biased [Pt (5 Angstrom)/Co (4 Angstrom)](3)/NiO (11 Angstrom) multilayer with perpendicular easy axis. Both the exchange field H-E and coercivity H-C display a closely linear temperature dependence except at very low temperatures. A thin NiO layer coated on the top of a Pt/Co multilayer has a great effect on the domain pattern of the Pt/Co multilayer, which is in a more irregular configuration with much smaller domain sizes than the uncoupled Pt/Co multilayer. A simulation according to Malozemoff's random field model gives a good agreement to the experimental temperature dependence of H-E and H-C, suggesting that the closely linear temperature dependences of H-E and H-C are strongly related to the behavior of the temperature of anisotropies and of the spin rotation inside the domain walls of a thin NiO layer. The blocking temperature of T-B=220 K is much higher than that observed in ferromagnetic/thin NiO systems with in-plane anisotropy. (C) 2003 American Institute of Physics.