Spin torque resonance has been used to simultaneously probe the dynamics of a magnetic domain wall and of magnetic domains in a nanostripe magnetic tunnel junction. Due to the large associated resistance variations, we are able to analyze quantitatively the resonant properties of these single nanoscale magnetic objects. In particular, we find that the magnetic damping of both the domains and the domain wall is doubled compared to the damping value of the host magnetic layer. We estimate the contributions to the damping arising from the dipolar couplings between the different layers in the junction and from the intralayer spin pumping effect, and find that they cannot explain the large damping enhancement that we observe. We conclude that the measured increased damping is intrinsic to large amplitudes excitations of spatially localized modes or solitons such as vibrating or propagating domain walls.
References
The 5 nm Py free layer is considered with a cell size of 4.4 nm × 4.4 nm × 5 nm (where the shape corresponds to the SEM image of Fig. 1). The magnetic parameters are: Ms = 0.47 MA/m, α = 0.01, and A = 13 pJ/m and the spin transfer torque parameters are the current polarization of 0.3 and field-like to Slonczewski torque ratio of 0.1.