A comparative study of write field distribution of trailing-edge shielded and unshielded perpendicular write heads by quantitative magnetic force microscopy

Abstract

Three-dimensional write field distributions of trailing-edge shielded and unshielded perpendicular write heads with applied direct current write currents were studied by magnetic force microscopy (MFM) measurements. A quantitative MFM approach of two times integrating measured frequency shift at a series of tip scan heights over the perpendicular direction was proposed to measure the magnetic field strength and field gradient. Results indicate shielded heads in addition to smaller saturation write currents, exhibited more than two to three times higher write field gradients over a wide range of moderate field strength over unshielded heads, thus, producing sharper bit transition and improved signal to noise ratio as theoretically predicted.

Thermal effects induced lateral head shift of thermal flying height control perpendicular magnetic recording head

“…For the lower line scan rate case, the transition zones are too fast to be observed. This shift in the head position was also previously observed during MFM measurement of the head field distribution for the TFC PMR head as a dc write current was applied to the head [10]. The lateral shift could be due to asymmetry in head structure of the fabricated TFC PMR head and/or heating profiles.…”

“…Figure 2(a) shows a typical AFM image of the ABS view of an unshielded type [10] PMR head before thermal activation by heating current/writing current, showing the tiny main pole (in trapezoidal shape with a step of ∼7-8 nm high in the gap between return poles RP1 and RP2 and a footprint of ∼200 nm Wr "on"-"off" Wr "off"-"on" As shown in figure 1, the micrometre-sized heater elements were located near the write/read head elements and embedded into the insulating materials (Al 2 O 3 ) under the ABS. With thermal activation by either heating or writing currents, the heat would in principle be conducted and distributed outwards from the higher temperature centre to lower temperature regions; while at the same time, the expansion of the heated region, both vertically and laterally, occurs.…”