This interview centers on the development of the MgO tunnel barrier used in modern TMR heads. Hard disk drives have survived as the information storage density device of choice because of sustained and steep advances in storage density. Density advances required downward scaling of key components. The reduction of the size of stored bits caused signal amplitude reduction which necessitated the invention of more powerful detectors. Magnetoresistive heads were the successful answer.
The third generation of MR heads introduced the phenomenon of tunneling to increase the change of resistance. The largest change of TMR head resistance has been achieved with the MgO tunnel barrier. This oral history records a history of the development of the polycrystalline MgO based magnetic tunnel junction and the contributions to its success by Messrs. Naoki Watanabe, Hiroki Maehara, Koichi Terunuma and Chang Man Park.