Condensed Matter Seminar Series
Manipulating Nanomagnets with Spin-Polarized Currents
Dan Ralph
Cornell University
Thursday October 14, 11:00 am, Room 234, Physics Building
Host: Albert Chang
Abstract: When a spin-polarized current interacts with a magnet, it can
transfer spin angular momentum to the magnet and thereby apply a
torque. This spin-transfer effect can be used to manipulate the
magnetic-moment direction of magnets without using magnetic fields. I
will discuss the microscopic origin of this effect and the dynamical
consequences for small magnets. Spin transfer from a DC current can
be used to produce magnetic reversal or to excite steady-state
precessional modes. We have determined the dynamical phase diagram
for the different types of modes that can be excited by measuring the
spectra of the microwave signals produced by the magnets when they
precess. In addition, recent time-domain measurements enable us to
determine the transient dynamics for a nanomagnet in response to
pulses of spin-polarized current. I will summarize progress in
developing spin-transfer devices for applications such as
non-volatile magnetic memory and frequency-tunable nanoscale
oscillators for signal processing.