Boson Green's functions treatment of three-layer ferrimagnetic superlattice [Comment on "Magnon energy gap and the magnetically structural symmetry in a three-layer ferrimagnetic superlattice", phys. stat. sol. (b) 243, No. 8, 1983-1995 (2006)]

Abstract

A magnetic superlattice with three-layer (plane) unit cell was treated within the boson formalism. The energies were derived using Green's functions formalism, and it is shown that previous calculations did not take into account the principal demand that excitation energies should be positive, so many previous conclusions should be re-examined. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.