Current induced multi-mode propagating spin waves in a spin transfer torque nano-contact with strong perpendicular magnetic anisotropy

Highlights: • Current induced spin wave excitations in an in-plane magnetized spin transfer torque nano-contact with a strong perpendicular magnetic anisotropy (PMA) is studied by means of micromagnetic simulations. • Our results indicate that broken spatial symmetry around the nano-contact induced by the Oersted field of the DC current let the system to excite two distinct propagating spin waves. • Presence of a strong PMA in the system prevents the formation of a spin wave soliton. • The propagating nature of the excited spin waves is an interesting feature for nano-scale magnonic crystals and waveguides. Current induced spin wave excitations in spin transfer torque nano-contacts are known as a promising way to generate exchange-dominated spin waves at the nano-scale. It has been shown that when these systems are magnetized in the film plane, broken spatial symmetry of the field around the nano-contact induced by the Oersted field opens the possibility for spin wave mode co-existence including a non-linear self-localized spin-wave bullet and a propagating mode. By means of micromagnetic simulations, here we show that in systems with strong perpendicular magnetic anisotropy (PMA) in the free layer, two propagating spin wave modes with different frequency and spatial distribution can be excited simultaneously. Our results indicate that in-plane magnetized spin transfer nano-contacts in PMA materials do not host a solitonic self-localized spin-wave bullet, which is different from previous studies for systems with in plane magnetic anisotropy. This feature renders them interesting for nano-scale magnonic waveguides and crystals since magnon transport can be configured by tuning the applied current.