Understanding field rise time and magnetic damping in thin film recording heads

Abstract

Magnetization dynamics during field reversal in thin film recording heads are studied via micromagnetic modeling. It is found that head field reversal under the current field can be characterized by two stages: an initial stage that is mainly governed by the gyromagnetic motion and virtually independent of energy damping, followed by a damping stage that strongly depends on the energy damping constant. Due to the finite energy damping in practical recording heads, the head field amplitude will roll off at high recording frequencies. Simply decreasing the current rise time or increasing current amplitude will not alleviate the situation, but rather worsen it. There exists an optimum current rise time at which the head field rise time is minimized and the roll-off frequency is maximized.

Experimental study of the head/medium magneto dynamics in perpendicular recording

“…Experimental work so far, to the best of our knowledge, has been limited to the write current wave forms with rise-times of about 1 ns. At this excitation speed and for a typical damping constant a ¼ 0:02 for the SUL the reversal process is still expected to be adiabatic [5,6], i.e., no excitation of spin wave modes should occur. For future high data rate recording products the write field rise-times of as small as 100 ps will be required.…”

Magnetic field measurement for analysis of GHz response in SPT head using electron beam tomography

“…Eddy currents and magnetization dynamics in the yoke may be limiting factors at over 1 GHz [3,4]. Timeresolved Kerr microscopy had been used to evaluate high-frequency head response [5][6][7], but the dimensions of the magnetic pole in present write heads are less than the optical diffraction limit.…”