Coherent Suppression of Magnetization Precession in Presence of Spin Waves in a ${\hbox {Ni}}_{81}{\hbox {Fe}}_{19}$ Microwire

In this paper, we present the coherent suppression of precessional dynamics in a Ni₈₁Fe₁₉ (permalloy) microwire of 12-mum width and 100-mum length in presence of multiple spin-wave modes. The lateral confinement of the microwire causes spin-wave modes of frequencies very close to each other and local suppression of the modes were experimentally achieved with field pulses of slightly different durations but with the same rise time and fall time. Analysis shows that application of the pulsed field causes a large angle reorientation of the magnetization followed by a precession. The termination of the pulsed field at around 500 ps causes the magnetization to return back to the equilibrium position and to align parallel to the effective field so that the torque on the magnetization vanishes. However, this applies only to localized regions due to the presence of spin-wave modes of slightly different frequencies. Pulses of slight under or over width cause the precession to continue at a slightly different frequency suggesting that the spin-wave modes are not truly localized but there are overlapping regions where one mode dominates. When the dominating mode is partially suppressed, the relative amplitude of the modes changes significantly and the overall power spectrum peaks at a slightly different frequency.