Spin wave excitation patterns generated by spin torque oscillators

Spin torque nano oscillators (STNO) are nano-scale devices that can convert a direct current into short wave-length spin-wave excitations in a ferromagnetic layer. We show that arrays of STNO can be used to create directional spin-wave radiation similar to electromagnetic antennas. Combining STNO excitations with planar spin waves also creates interference patterns. We show that these interference patterns are static and have information on the wavelength and phase of the spin waves emitted from the STNO.We describe means of actively controlling spin-wave radiation patterns with the direct current owing through STNO, which is useful in on-chip communication and information processing and could be a promising technique for studying short wave-length spin waves in different materials.