The effect of the Bsof recording head cores on the magnetization of high coercivity media

Two types of recording heads, the cores of which had different values of saturation flux density B
s
and almost the same values of effective permeability, were prepared and the recording characteristics with Ni-Co plated discs of varying coercivity H
c
(410-900 Oe) were examined. The materials of the head cores were a sputtered alloy (Fe-Si-Al) film (
B_{s} = 11 000
G) and a single crystalline Mn-Zn ferrite (
B_{s} = 3800
G). Results showed that the B
s
of the head core had to be about five times the H
c
of the media to produce the beneficial effects of high H
c
on short wavelength recording. From this point of view, the alloy film head has the advantage in high linear density recording because of its large B
s
. By using an experimental laminated alloy film head of narrow-track width (60 μm), the core of which had a large effective permeability (such as 115 at 40 MHz), sine-wave signals of short wavelength (smaller than 1.5 μm) and of high frequency (such as 37 MHz) were recorded on a high H
c
(900 Oe) plated disc and reproduced with the same head successfully.