Yoshio Tawara

Permanent magnets based on (Ce,Sm)(Co,Fe,Cu)z

RTz alloys known as permanent magnet materials were reexamined with particular emphasis on Ce‐rich compositions. Performance of Ce‐based alloys was much improved by changing the transition‐metal compositions from conventional ones. The Ce‐based alloys exhibited 14.8 MG Oe of maximum energy product. Use of Sm, not exceeding 30% of the total rare earths, resulted in even higher energy, up to 17 MG Oe.

Single crystal silicon substrate for magnetic rigid disk

The advance in high density recording with magnetic rigid disk continuously requires substrate having better properties, such as higher thermal stability, higher hardness, lower specific gravity, smoother surface, and so on. Single crystal silicon is one of the best candidate material to meet the requuements. The newly developed process to fabricate 1.8 inch subsuate from 6 inch diameter silicon ingots as available in the semiconductor market will be presented. Combining this technology with the well-established fabrication method of silicon wafer widely used in semiconductor devices such as LSI, we can provide high grade single crystal silicon substrates for rigid disks. Precise dimensions with close tolerances and extremely flat and smooth surface have been achieved. The new process will also help to reduce the price level to the range feasible for practical use.