Two modes behavior of vortex oscillations in spin-transfer nanocontacts subject to in-plane magnetic fields
Michaela Kuepferling, Claudio Serpico, Matthew Pufall, William Rippard, Thomas Mitchell (Mitch) Wallis, Atif A. Imtiaz, Pavel Kabos
The field dependence of vortex oscillations in a spin-transfer metallic nanocontact, subject to in-plane, spatially uniform, external fields, is studied by measuring the power spectral density of the voltage across the device. The measured spectra as a function of the DC current (Idc) indicate a transition between two oscillation modes. The two modes are distinguished by their different values of dfosc=dIdc and their different dependence of fosc (oscillation frequency) on the external field. The field dependence of the low frequency/low current mode indicates the presence of a quasiuniform magnetization configuration in one of the layers whereas the substantial insensitivity to the field dependent of the high frequency/high current mode indicates the presence of vortices in both layers. For intermediate values of Idc these two modes coexist giving rise to doubly peaked spectra. It is discussed that the experimental data are compatible with a dynamical coupling of the two ferromagnetic layers due to spin-torque and the coupling principle that leads to vortex oscillations is described qualitatively.
, Serpico, C.
, Pufall, M.
, Rippard, W.
, Wallis, T.
, Imtiaz, A.
and Kabos, P.
Two modes behavior of vortex oscillations in spin-transfer nanocontacts subject to in-plane magnetic fields, Applied Physics Letters, [online], https://doi.org/10.1063/1.3455883
(Accessed March 1, 2024)