Current-Driven Microwave Dynamics in Magnetic Point Contacts as a Function of Applied Field Angle
William H. Rippard, Matthew R. Pufall, Shehzaad F. Kaka, Thomas J. Silva, Stephen E. Russek
We have measured microwave frequency, current-driven magnetization dynamics in point contacts made to Co90Fe10/Cu/Ni80Fe20 spin valves as a function of applied field strength and angle relative to the film plane. As the field direction is varied from parallel to nearly perpendicular, the device power output increases by roughly two orders of magnitude while the frequencies of the excitations decrease. For intermediate angles the excited frequency does not monotonically vary with applied current and also exhibits abrupt, current-dependent jumps. For certain ranges of current, and applied field strength and direction, the excitations linewidths decrease to a few megahertz, leading to quality factors over 18 000.
Physical Review B (Condensed Matter and Materials Physics)