Nonreciprocal Spin Waves in a Magnonic Crystal with In-Plane Static Magnetization

It is shown that spin waves propagating in a planar periodic array of dipolarly coupled magnetic strips or dots with in-plane static magnetization can be nonreciprocal. The conditions of the spin waves nonreciprocity are: (i) breaking of the mirror symmetry of an array with respect to its plane, and (ii) complex structure of the array lattice. These conditions can be satisfied, e.g., if an array consists of at least two groups of strips (dots) having different thicknesses (heights). The largest nonreciprocity can be achieved if the static magnetic state of an array is antiferromagnetic, and the difference in the strip thicknesses is about two times. A significant dependence of the spin wave nonreciprocity on the static magnetic state of a strip array allows one to create magnonic crystals with reconfigurable nonreciprocal properties.