Performance of dual-stripe giant magnetoresistive heads on tape

Dual-stripe giant magnetoresistive (DSGMR) devices with an insulating spacer were fabricated and tested on tape media. The head design consists of two mutually biased, unshielded GMR elements based on [Cu 19 Å/NiFe 13 Å/CoFe 4Å]_×10 antiferromagnetically coupled multilayers, separated by a 600-Å-thick SiO₂ spacer. The sensor is patterned into a U shape, with leads connected away from the active region to avoid topography. Simultaneous etching of both GMR elements avoids misalignment problems along or across the track width. A DSGMR tape head operating in differential mode (track width of 2 μm and height of 0.8 μm) was tested versus high density dibits (0.05<bit<4 μm) recorded on tape media, using a current bias of J=2.8×10⁷ A/cm² on each GMR. The DSGMR responds to the dibit with a bipolar pulse independently of bit separation even when the individual GMR elements are partially saturated. Peak-to-peak output is 1.7 mV/μm, for bit sizes ⩾0.4 μm. Experimental pulse amplitude and shape are in agreement with a two-dimensional micromagnetic simulation. The head response to a dibit signal loses half its maximum amplitude for a recorded bit size of 0.2 pm. Pulse broadening (read bit cell is 0.8 μm larger than recorded bit, for bit sizes <0.4 μm) is correlated with sensor geometry