The Role Of Boron On Exchange Coupling In Nife/Ru1-Xbx/Feco Trilayer Structures

D In this work, we study the interlayer exchange coupling, J, between two NiFe and FeCo layers in a series of NiFe=Ru(1-x)Bx(d)=FeCo synthetic antiferromagnet (SAF) samples, where the thickness of the spacer layer, d, is varied from 0.4 nm to 0.9 nm, and the boron concentration, x, is varied from 0 to 15 at. %. The samples are studied as deposited and after being annealed at 250 degrees C. B is deposited into the Ru spacer layer to investigate what occurs after annealing a FeCoB/Ru/FeCoB SAF structure, which is commonly used in modern nanoscale magnetic devices, in which the FeCoB layer crystallizes to FeCo and B diffuses to adjacent layers. We find that J in as-deposited samples is relatively unaffected by adding up to 15% B into the Ru spacer layer. However, after annealing at 250 degrees C, J changes the sign from antiferromagnetic coupling to ferromagnetic coupling for spacer layers thinner than 0:45 nm for 5% and 10% B and thinner than 0:525nm for 15% B. We used transmission electron microscopy energy-dispersive x-ray spectroscopy in order to investigate the diffusion of atoms within a similar Ta(2:5 nm)=NiFe(0:8 nm)=Ru(1-X)Bx(23 nm) layer structure. We find that after annealing at 250 degrees C, the sample containing 15% B within the Ru85B15 layer had significantly more diffusion of Fe into the Ru85B15 layer, from the NiFe layer, as compared to the sample with 0% B. Thus, the presence of B within the spacer layer enhances diffusion of Fe into the spacer layer.