A study of electrical charge at head-disk interface

The electrical charge at head-disk interface (HDI) of disk drives becomes increasingly important as head-disk spacing drops below 10 nm range. In this study, a new method of measuring electrical charge at HDI is presented. It involves measuring magnetic read-back signals (i.e. PW50), while the flying height (FH) is lowered by electrostatic force. Typical HDI charges are in the range of –0.2 to –0.9 V, depending on individual head–disk combination. Experiments were also conducted to eliminate the HDI charge by using an ionizer and surface treatment of magnetic heads. It was found that the HDI charge can be effectively eliminated by treating the magnetic head with a fluorinated carbon coating. The mechanisms of HDI charge generation and elimination are discussed.