Magnetic instability of thin-film recording heads

Two forms of magnetic head instability are investigated: Write and read instability. Write instability generates noise directly after writing which impairs sector-servo performance. This noise peaks at write currents saturating the apex or backgap. The noise amplitude is exponentially distributed. The noise is caused by cooling off of the yoke after write as well as by thermally activated domain wall jumps in the upper yoke. Read instability produces read pulse distortion, predominantly on the signal´s trailing edges. The only form of instability in dedicated-servo drives, read instability is best characterized by pulsewidth measurements. The degree of instability changes with intermediate writes. Read instability is caused by hysteretic domain wall motion in the pole tips in response to signal excitation and/or stray magnetic fields