The effect of the B<inf>s</inf>of recording head cores on the magnetization of high coercivity media

Abstract

Two types of recording heads, the cores of which had different values of saturation flux density B <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</inf> and almost the same values of effective permeability, were prepared and the recording characteristics with Ni-Co plated discs of varying coercivity H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> (410-900 Oe) were examined. The materials of the head cores were a sputtered alloy (Fe-Si-Al) film ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B_{s} = 11 000</tex> G) and a single crystalline Mn-Zn ferrite ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B_{s} = 3800</tex> G). Results showed that the B <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</inf> of the head core had to be about five times the H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> of the media to produce the beneficial effects of high H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> 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 <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</inf> . 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 <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> (900 Oe) plated disc and reproduced with the same head successfully.