Comment on "Thickness dependence of exchange bias and coercivity in a ferromagnetic layer coupled with an antiferromagnetic layer" [J.Appl.Phys. 94, 2529 (2003)]

Abstract

Hu, Jin, and Ma have proposed a theoretical investigation on the influence of the antiferromagnetic layer thickness on the magnetic properties of ferromagnetic/ antiferromagnetic bilayers [J. Appl. Phys. 94, 2529 (2003)], considering both the bilinear and biquadratic exchange couplings, and have claimed that from their formulas for the hysteresis loop displacement and coercivity many interesting conclusions can be extracted. Unfortunately, the mathematical procedure used to find the equilibrium of the system is based on inadequate stability conditions and has led to nonphysical results. More importantly, the simple phenomenological model, employed by the authors, is intrinsically not capable to give the antiferromagnetic layer thickness dependence of the magnetic properties of such exchange-coupled bilayers.