Thickness dependence of spin wave nonreciprocity in permalloy film

Abstract

The amplitude of the spin wave (magnetostatic surface spin wave) depends on the propagation direction. Nonreciprocity hardly depends on the permalloy (Py) thickness between 100 and 300 nm, and it is determined by the spin wave resonant frequency. The nonreciprocal parameter decreases with increasing frequency, resulting in the large amplitude asymmetry at high frequencies, which is well supported by a result of theoretical analysis. The nonreciprocity of a 25-nm-thick-film, however, is lower than those of thicker films. This is qualitatively explained by a schematic model based on the origin of nonreciprocity.