Spin-torque-driven
ferromagnetic resonance (STT-FMR)
PAPER: T. Staudacher and M. Tsoi,
“Spin-torque-driven ferromagnetic
resonance in point contacts”,
J. Appl. Phys. 109,
07C912 (2011).
SLIDES: 55th
Magnetism and Magnetic Materials Conference
ABSTRACT:
We demonstrate the technique of
spin-torque-driven ferromagnetic resonance (STT-FMR) in point contacts, which
enables FMR studies in sample volumes as small as a few cubic nanometers. In
our experiments, we use point contacts ~10 nm in size to inject both dc and
microwave currents into F/N/F/AFM exchange-biased spin valves where two
ferromagnetic (F) layers are separated by a nonmagnetic (N) metal spacer and
one of the Fs is pinned by an adjacent antiferromagnetic
(AFM) layer. High current densities produce the spin-transfer torque on
magnetic moments in a small contact region and drive it to resonance at
appropriate frequency of the applied microwaves. The resulting magnetodynamics are detected electrically via a small
rectified dc voltage, which appears across the contact at resonance. The width
of the resonance varies linearly with the applied dc bias as expected for spin
transfer in spin valves. Potentially, the point-contact technique extends the applicability
of ST-FMR to higher/lower frequencies, smaller sample volumes, and a broader
range of materials.
This work was supported
in part by NSF Grant DMR-06-45377