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3885Absrrucr -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 a s 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 w a s f u r t h e r 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 p r o b a b i l i t i e s .

Correlation between noise-after-write and magnetization dynamics i n 30-turn electroplated thin film heads has been investigated by utilising two complementary magneto-optic Kerr effect domain imaging systems and a Barkhausen noise tester. It has been found that heads containing spike-like domains near the backgap closure have significantly higher noise-after-write rates than heads with normal closure domain configurations. A longitudinal 180° wall in the direction of flux conduction at the sloped region of the pole tip was observed, however, independent of whether the head had a high or low noise-after-write rate.

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---The effects of thermal transients after write, changes in stress-magnetostriction products and dynamic domain instabilities on popcorn noise probabilities in micro Flexhead® components were studied., It was observed that popcorn noise probabilities in micro Flexhead® components increase as the write current duration increases, until they saturate, with a specific write current amplitude. With increasing write current amplitude, the initial rate of change of noise probability with write current duration increases. In some cases where the resultant stress-magnetostriction products in micro Flexhead® components are negative, popcorn noise probabilities were observed to increase exponentially as functions of applied stress gradients. High rates of occurrence of dynamic domain instabilities have also been correlated with micro Flexhead® components that have high popcorn noise probabilities. Therefore. high probabilities of popcorn noise in micro Flexhead® components are caused by the combined effects of thermal transients after write, changes in stress-magnetostriction products and dynamic domain instabilities. Finally. an inductance fluctuation measurement technique was shown to be useful in quickly detecting micro Flexhead® components that are susceptible to popcorn noise.