Spin-Transfer-Torque:
Ferromagnets
An electrical current can transfer spin angular
momentum to a ferromagnet [1–3]. This novel physical phenomenon, called spin
transfer (or spin torque), offers unprecedented spatial and temporal control
over the magnetic state of a ferromagnet and has tremendous potential in a
broad range of technologies, including magnetic memory and recording. Here we describe
several spin-transfer-torque studies, starting with the first observation of
the phenomenon [3] in Co/Cu multilayers.
Co/Cu Magnetic Multilayers Original observation of spin transfer
Current-Driven Excitations in
Symmetric Magnetic Nanopillars STT-induced
excitations of both F-layers in F/N/F trilayers
Probing Wavenumbers of
Current-Induced Excitations in Point-Contact Experiments Tuning wavelength of STT excitations
Current-sweep-rate dependence of spin-torque
driven dynamics in magnetic nanopillars Exploring the onset of STT
excitations
Spin-Torque-Driven Ferromagnetic Resonance STT-induced ferromagnetic resonance (FMR) in point
contacts
Spin-Torque-Driven Parametric Resonance STT-induced parametric resonance in point contacts
An electrical current can affect the magnetic state of
a ferromagnet in a number of ways. In addition to inducing spin waves,
precession, and reversal of magnetization, a spin-polarized current was
predicted to apply a torque to a magnetic domain wall [4]. The following
projects investigate the dynamics of magnetic domain walls subject to field-
and current-induced torques.
Field-driven dynamics of domain
walls in ferromagnetic nanowires
Current-driven dynamics of domain
walls in ferromagnetic nanowires STT
effect on magnetic dynamics of individual domain walls
Universal electromotive force induced by
domain wall motion The reverse of
STT effect
1.
Slonczewski, J. C. Current-driven excitation of magnetic
multilayers. J. Magn. Magn. Mater. 159, L1-L7 (1996).
2.
Berger, L.
Emission of spin waves by a magnetic multilayer traversed by a current. Phys. Rev. B 54, 9353-9358 (1996).
3.
Tsoi, M. et al. Excitation of a magnetic
multilayer by an electric current. Phys.
Rev. Lett. 80, 4281-4284 (1998).
4.
Berger, L. Low-field magnetoresistance and domain drag in
ferromagnets. J. Appl. Phys. 49, 2156 (1978).