Magnonic crystal theory of the spin-wave frequency gap in low-doped manganites

A theory of three-dimensional (3D) magnonic crystal (conceived as the magnetic counterpart of the photonic crystal) is developed and applied to explain the existence of the spin-wave frequency gap, recently revealed by neutron scattering experiments, in low-doped La1-xCaxMnO3 manganites. A confrontation of the theory with experimental results proves that certain manganites can be regarded as 3D magnonic crystals existing in the nanoscale in nature. (c) 2006 American Institute of Physics.