Pressure-induced signal loss in Fe3O4and γ-Fe2O3thin film disks

Pressure-induced signal loss in Fe
3
O
4
and γ-Fe
2
O
3
thin film disks has been investigated. Through gauzes, pressure of 20 to 500 g/cm
²
were applied to the surface of a disk rotating 300 revolutions per minute (rpm). The result was extremely large signal losses of 40 to 90 percent. Several types of losses characteristic of ferrite surfaces were observed: initial loss, subsequent loss, and steady loss. These phenomena were consistently explained by a model that shows that the removal of a small amount of unstable surface crystallites by pressure reduces the leakage flux density. Wiping the rotating disk surface with gauze at a pressure of about 1000 g/cm
²
was effective in reducing the loss. It was confirmed that Ti doped γ-Fe
2
O
3
thin films prepared from α-Fe
2
O
3
show better resistance to pressure than do Fe
3
O
4
and other γ-Fe
2
O
3
films. Surface lubrication of the medium was also confirmed to be effective in reducing the loss. Contact-start-stop (CSS) induced signal loss and the possibility of pressure-induced missing signal errors due to thin film pinholes were also examined for typical γ-Fe
2
O
3
thin film disks.