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
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