Write frequency dependence of popcorn noise in GMR heads

Popcorn noise of integrated inductive write/GMR read heads was characterize d at various write currents and frequencies. The popcorn noise count tends to increase with write current and peaks at a certain frequency, This was a ttributed to heating-cooling cycles of heads induced by the write current, which rolls off with frequency. In fact, it was observed that write current heating peaks around the same frequency. The heating is caused by Joule he ating of writer coils and eddy current loss of the writer core. A larger po pcorn count was observed if the heat diffusion path is restrained, for exam ple, by unloading heads from the media surface. The clock frequency at whic h the popcorn noise peaks is higher when tested with a pseudo-random write pattern instead of a single frequency pattern. Potential impact of high dat a rate and write current rise time of preamplifiers is discussed.