Until recently, the only means known to control the magnetization state of ferromagnetic structures was through the use of applied magnetic fields. However, within the last several years it has been demonstrated that this can also be accomplished through the transfer of the electron spin angular momentum from current-carrying electrons to the magnetization of magnetic films, generally referred to as the spin-momentum-transfer effect. Spin transfer represents a fundamentally new way to control and manipulate the magnetic states of devices, and allows hysteretic switching and coherent microwave dynamics to be excited in magnetic nanostructures using a DC current. This project seeks both to understand the fundamental characteristics of the interaction between spin polarized currents and magnetic materials, and also to examine the suitability of such nanoscale devices for microwave electronics. We are specifically pursuing research in (1) increasing output power from nanoscale oscillators through materials engineering and incorporating tunnel junctions into the device structures, (2) understanding the interactions between mutually synchronized nanoscale oscillators in order to develop device arrays, (3) characterizing and understanding the thermal contributions to both oscillator linewidths and the current induced switching distributions in patterned elements, (4) understanding the interactions between individual magnetic nanostructures and AC fields and AC currents, and (5) investigating the current-induced switching properties of patterned magnetic nanostructures for magnetic random-access memory applications.
Magnetism; Magnetodynamics; Microwave circuitry; Nanotechnology; Spin electronics; Spintronics;