Effect of film microstructure on exchange bias of IrMn/CoFe films

In order to isolate the effects of IrMn film grain size, texture and roughn ess on the temperature dependence of exchange bias field (H-ex) different m ultilayers of the configuration UL/CoFe4/IrMn5/Ta3nm (top) and UL/IrMn5/CoF e4/Ta3nm (bottom) were deposited, Underlayers (UL) used were Cu, Ru and [Cu 1/Ru1nm]n with thickness varying between 5-100 nm. The H-ex vs. temperature curve shows a change in shape from a convex type to concave type with incr easing the grain size, A qualitative explanation is given based on a therma l fluctuation after effect model.