Linear and nonlinear excitation of magnons by electron spin injection in thin ferromagnetic films

Experiments are reviewed in which strong linear excitation of magnons by ac currents in Fe/Cr/Fe trilayers are observed through Brillouin light scatte ring. The scattering intensity is investigated as a function of the magnon wave number and applied magnetic field, thus providing strong evidence for electronic spin injection in the rf driving field. In addition, model calcu lations are presented for the post-threshold dynamics of the magnetization in an electron-spin-injection field induced by a dc current. It is shown th at the interaction between the driven modes may lead to hi-ah-frequency osc illatory instabilities and universal chaotic phenomena, adding intriguing s imilarities between the laser and the recently proposed spin-wave maser or swaser.