Dynamic domain instability and popcorn noise in thin-film heads

Abstract

The effects of dynamic domain instability on popcorn noise probabilities were studied by correlating the measured popcorn noise probabilities with the instantaneous observations of dynamic domain states of thin-film heads during and after writing. Heads with large peak popcorn noise probabilities at intermediate values of write current amplitude were observed to exhibit asymmetric domain patterns and occasional popping wall motion in the yoke structure during writing. The occurrences of dynamic domain instability were imaged by comparing many instantaneous domain patterns at 10 μs after a specific write current excitation. Delayed-relaxation Barkhausen wall jumps near the backgap closure were observed occasionally in several noisy heads. Quantitative correlation between the probabilities of popcorn noise and dynamic domain instability was also obtained in a very noisy head. Dynamic domain instabilities in the yoke are thus responsible for the peak popcorn noise probabilities in thin-film heads.