Spin wave dynamics in two- and three-dimensional superlattices of nanosized ferromagnetic spheres

Abstract

The dispersion of spin wave modes which due to the dipolar interactions propagate along different directions of ordered superlattices of nanospheres is investigated. For this purpose a procedure similar to the well-known method of linear combination of atomic orbitals is applied. Different geometries of two-dimensional (triangular and square) and three-dimensional (simple cubic and hexagonal-close-packed) arrangements are considered and the influence of dimensionality on the spin wave dynamics is analyzed. A phase transition which is caused by the competition between dipolar and uniaxial anisotropy interactions is predicted by the investigation of the dispersion of the uniform Kittel mode for the superlattice of the hexagonal order. In conclusion, it is shown how the weak dipolar interaction enhances or decreases the relaxation time in the samples with a controlled direction of the easy axis.