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).
Supported in part by NSF grant DMR-06-45377