Magnetic characterization of exchange-coupled thin films having competing anisotropies

We have studied the magnetic properties of co-sputtered Ni0.89Fe0.11 single layers (10-100 nm) and Ni0.89Fe0.11/Ni0.89Fe0.11 bilayers (10 nm/10nm to 100 nm/100 nm) grown on glass substrates. Hysteresis loops and transverse biased initial susceptibility measurements were performed by transverse magneto-optical Kerr effect from both film/air and film/glass interfaces. The individual layers show in-plane uniaxial easy axes produced by the oblique incidence of incoming atom beams. For thinner bilayers (up to 20 nm/20 nm) the overall magnetic behavior can be justified by competing effective uniaxial and biaxial anisotropies acting over the average magnetization. For thicker bilayers (40 nm/40nm and above), both transverse magneto-optical Kerr effect measurements and micromagnetic simulations suggest the existence of a Bloch-type magnetic wall extending across the thickness of the bilayer. (c) 2007 Elsevier B.V. All rights reserved.