Excitation of spin waves by a current-driven magnetic nanocontact in a perpendicularly magnetized waveguide

It is demonstrated both analytically and numerically that the properties of spin wave modes excited by a current-driven nano-contact of length L in a quasi-one-dimensional magnetic waveguide magnetized by a perpendicular bias magnetic field He are qualitatively different from the properties of spin waves excited by a similar nano-contact in a two-dimensional unrestricted magnetic film (“free layer”). In particular, there is an optimum nano-contact length Lopt corresponding to the minimum critical current of the spin wave excitation. This optimum length is determined by the magnitude of He, the exchange length and the Gilbert dissipation constant of the waveguide material. Also, for L < Lopt the wavelength λ (and the wave number k ) of the excited spin wave can be controlled by the variation of He (λ decreases with the increase of He ), while for L > Lopt the wave number k is fully determined by the contact length L (k~1/L) , similar to the case of an unrestricted two-dimensional “free layer”.