Inductance fluctuation, domain instability and popcorn noise in thin film heads

The mechanisms of popcorn noise in thin film heads were studied by correlating the inductance fluctuations under DC bias current, domain instabilities after write and popcorn noise probabilities. Inductance fluctuations of heads were obtained by calculating the standard deviations of the inductance values measured from 20 traces by a HP network analyzer. Instantaneous domain patterns during and after write as well as popcorn noise probabilities of heads were observed by a 0.5-nsec exposure time wide-field Kerr effect microscope and a Barkhausen noise tester, respectively. A strong correlation was found among inductance fluctuations, domain instabilities and popcorn noise probabilities in a noisy head. This relationship was further confirmed by the quantitative correlation between the peak popcorn noise probabilities and peak inductance fluctuations of 12 different heads. Therefore, by measuring the inductance fluctuations of thin film heads under DC bias current, one can infer their susceptibilities to Barkhausen wall jumps, and thus popcorn noise probabilities