New Mn-Zn ferrite fabricated by hot isostatic pressing

A hot isostatic press (HIP)technology for Mn-Zn ferrite has been investigated to meet material requirements of recording head applications; i.e. pore-free and uniform fine grain size. Pore-free materials can be fabricated by HIP technology at relatively low temperatures. HIP´ed ferrite have fine grain sizes which are effective for high-frequency properties and machinability. The Mn-Zn ferrite is densified to a pore-free state with use of the presintered specimen having the density more than 95% of the theoretical value without encapsulating. A temperature in HIP stage should be, lower than a temperature in presintering to obtain the uniform grain size. IBM 3350 type head with 10μm track width were fabricated from a HIP´ed Mn-Zn ferrite having saturation induction of 0.51T, permeability at 5MHz of 750 and average grain size of 8μm. These heads were examined on recording performance using a plated disk with a coercivity of 78000A/m and a thickness of 0.03μm. Superior writing performances, write-over of -35dB and minimum saturating mmf of 0.35A, were attained. A read signal improvement over typical Ni-Zn heads was 50% at a recording density of 700 FRPM (18000 BPI).