Localized Defect Modes in a Two-Dimensional Array of Magnetic Nanodots

The microwave properties of an array of magnetic nanodots in a ferromagnetic state having a point defect-a dot with inverted magnetization or different material parameters-are considered. The existence of a single-point defect in a dot array may lead to the appearance of several localized modes: one “defect eigenmode” and several “well modes,” the number and structure of which strongly depend on the magnetostatic interactions between the dots. By performing a ferromagnetic resonance experiment on an array of magnetic dots containing a small number of defects, it is possible to obtain information about the entire spin-wave spectrum of the array.