Current-Driven Microwave Dynamics in Magnetic Point Contacts as a Function of Applied Field Angle

TL;DR

This study investigates how the microwave frequency and power output of magnetic point contacts change with applied magnetic field angle, revealing significant variations in dynamics, frequency behavior, and linewidths.

Contribution

It provides new insights into the dependence of microwave magnetization dynamics on field angle and current in spin valve point contacts, including high-quality factor excitations.

Findings

Power output increases by two orders of magnitude with field angle change.

Excitation frequencies decrease as the field angle approaches perpendicular.

Linewidths can be reduced to a few megahertz, achieving high quality factors over 18,000.

Abstract

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 excitation linewidths decrease to a few megahertz, leading to quality factors over 18,000.