Head-disk contact detection using a thermal sensor for modulation air bearings

An apparatus, comprising:

• a slider configured for writing data to and reading data from a magnetic recording medium, the slider configured for heat-assisted magnetic recording and comprising:
• a heater configured to receive an AC signal and to cause oscillation in a spacing between the slider and the medium;
• and
• a contact sensor situated on the slider and configured to produce a DC response signal;
• and
• a detector coupled to the slider and configured to measure an amplitude of a spike in the DC response signal, calculate a ratio between the spike amplitude and an amplitude of the DC response signal, and detect contact between the slider and the medium in response to the ratio exceeding a predetermined threshold.

An apparatus, comprising:

• a slider configured for writing data to and reading data from a magnetic recording medium, the slider configured for heat-assisted magnetic recording and comprising:
• a heater configured to receive an AC signal and to cause oscillation in a spacing between the slider and the medium;
• and
• a contact sensor situated on the slider and configured to produce a DC response signal;
• and
• a detector coupled to the slider and configured to:
• calculate an amplitude of a dR/dP curve developed using the DC response signals, where dR is a change in resistance of the contact sensor and dP is a change in heater power;
• measure an amplitude of a spike in the DC response signal;
• calculate the ratio as a ratio between the spike amplitude and the amplitude of the dR/dP curve;
• detect a minima of the dR/dP curve;
• and
• detect contact between the slider and the medium in response to either the ratio exceeding the predetermined threshold or detecting the minima of the dR/dP curve.