Microscopic manipulations of interatomic coupling density for tailoring of exchange bias mediated by mesoscopic interface topology

Abstract

Mesoscopic-scale effects of ferro-antiferromagnetic (F/AF) interface texture are simulated by an atomistic model, considering an exchange bias to be proportional to interfacial density of microscopic F-AF atomic coupled pairs. The model reveals a mediating role of crystalline growth direction on the exchange bias variability by other modifications of interface texture. By adjusting the number of the nearest neighboring atoms belonging to the interface plane, the growth direction defines topological possibility for exchange bias enhancement by roughness, as well as the range, within which the exchange bias can be tailored by substitutional defects. The model has been experimentally approved by investigation of exchange bias and texture modifications in a set of (0 0 1) and (1 1 1) textured NiFe/IrMn bilayers grown on Ta/Cu and Ta/Au hybrid seed layer stacks, respectively. The revealed variations of exchange bias with Au and Cu seed layer thicknesses are gradual, but have opposite signs. The result is well agreed with the simulated variability of coupling pair density for (0 0 1) and (1 1 1) interfaces. This confirms that crystallographic orientation of the F/AF interface plane sets topological possibility for tailoring the exchange bias by microscopic F-AF coupled pair density through mesoscopic modifications of the interface texture. © 2021 Elsevier B.V.