LIQUID-FILM-MEDIATED SCANNING THERMAL MICROSCOPY OF A MAGNETORESISTIVE READING HEAD

Magnetoresistive (MR) heads containing 45-nm-wide permalloy (NiFe) thi n pms require current densities on the order of 10(11) A/m(2) for read ing operation, resulting in heat generation rates of 10(15) W/m(3). Sc anning thermal microscopy (SThM) showed a maximum temperature rise of 20 degrees C, an average temperature gradient higher than 10(6) K/m, a nd heat flux Of 10(8) W/m(2) near the MR element. Topography-induced f eatures on the order of 20-25 nm in size were observed in the thermal images. Estimation of tip-sample thermal resistance, experiments in di fferent environments, as well as calculations of liquid film thickness and thermal resistance suggested that the dominant tip-sample heat co nduction was dominated by a liquid film bridge. This also explained th e topography-induced nanoscale thermal features.