Spin-Transfer Torque Driven Ferromagnetic Resonance In Nano-Contact Magnetoresistive Devices And Its Characteristics

We investigated the spin-transfer torque driven ferromagnetic resonance in nano-contact magnetoresistive (NCMR) devices with a current-perpendicular-to-plane spin-valve structure consisting of a FeCo layer, a FeCo-AlOx nano-oxide layer, a FeCo multilayer for the reference, a spacer, and free layers. In contrast with tunneling magnetoresistance devices with an AlOx spacer layer that shows a single resonant frequency, NCMR devices showed multi-resonant frequencies caused by free-layer resonance and other types of resonance appeared in a frequency region higher than that of the free-layer. We discuss these characteristic results in terms of the magnetic structure of the NCMR device, especially the free and reference layers around the nano-contacts. (C) 2011 American Institute of Physics. [doi:10.1063/1.3562511]