Materials Science Forum Vols. 302-303 (1999) pp. 64-75


Magnetic Multilayers: Interlayer Coupling in Fe/Cr/Fe

S.M. Rezende, C. Chesman, M. A. Lucena, M. C. de Moura, A. Azevedo and F. 
M. de Aguiar

The exchange coupling between neighbouring magnetic layers in multilayer 
system consisting of stacks of ferromagnetic layers separated by 
nonmagnetic metallic layers plays central role in the properties of these 
novel artifically structured materials. Here we review the most common 
techniques for measuring this couling, namely magneto-optical Kerr effect 
magnetometry, Brillouin light scattering and ferromagnetic resonance. The 
theoretical background for interpreting experimental data in trilayers 
formed by two magnetic layers separated by a nonmagnetc layer is 
presented, based on phenomenological model energy including bilinear and 
biquadratic exchange couplings, as well as surface, in-plane uniaxail and 
crystalline cubic anisotropy contributions. Accurate quantitative values 
for the coupling constants and the other magnetic parameters are measured 
in the prototype system (100) Fe/Cr/Fe grown by sputtering for several Cr 
spacer thickness. Consistent values are obtianed with all three 
techniquesd for both the bilinear (J1) and biquadratic (J2) exchange 
coupling constant. In most of the Cr thickness range corresponding to the 
first antiferromagnetic peak, J2 follows J1 with a ration J2/|J1|~0.1. In 
the range corresponding to the second antiferromagnetic peak J2 also 
follows J1, but with a much larger ratio J2/|J1|~1.0 indicating that the 
origin of the biquadratic coupling in the two ranges resides in different 
mechanisms.