Metal-in-gap record head

High density signal levels increase as the record head gap is reduced. When the gap is reduced, the optimum deep gap record field increases. With small gaps and high coercivity tapes, the wear resistant ferrites used to make standard heads saturate at the gap corners. This smears the record field gradient and performance suffers. Traditionally, the solution to this problem has been to make a ferrite core equipped with high saturation flux density Sendust pole tips. The record performance of tipped heads is excellent, but they are expensive and fragile because they are epoxied together, and their wear rate is much higher than ferrite heads. We have developed a process for vacuum depositing high permeability Sendust thin films on the gap faces of ferrite heads before gap spacer deposition. These metal in gap (MIG) heads can be glass bonded. The result is a long wearing, rugged, and inexpensive record head which gives optimum 80 KBPI performance on 860 Oe coercivity media using standard ferrite cores and gaps as small as 0.3μ. With a 250μ trackwidth, a tape speed of 19.1 cm/sec, and a frequency of 300 KHz (80 KFCI), MIG heads have achieved an RMS signal-to-wideband noise ratio of 30dB on high squareness isotropic tapes. Similar all-ferrite heads record only about half this signal. Construction and performance of MIG heads will be described.