Possibility as a magnetic recording media of austenitic stainless steel using stress-induced phase transformation

A new magnetic recording media which uses the phase transformation of austenitic stainless steel, is proposed. The transformation from austenite to martensite occurs due to tribological stresses, such as indentation and sliding, has the potential to induce phase transformation which in turn generates a locally ferro-magnetized surface. Surface observations were made using magnetic force sensing systems having a sensing mechanism similar to that of magnetic force microscope (MFM). Two-dimensional distribution of the magnetic force measured by the sensing systems showed many possible applications in magnetic recording, and magnetic field freezing, etc. Scratching experiments with a load of 0.4 mN verified the possibility of the material's application as a recording media with spatial resolution of submicrometer. Memorizing phenomena of magnetic field in a stainless steel plate was also observed. After a uniform tensile stress generated the phase transformation of a stainless steel thin plate in a magnetic field, the magnetic force distribution on the steel surface was measured. The distribution was similar to that of the magnetic field which was induced by an exciting coil. The results indicated that information about the external magnetic field distribution was frozen in the stainless steel test specimen. By using this phenomenon, an analogue-type recording system capable of memorizing a two-dimensional distribution of a magnetic field at any arbitrary point in time by an external force trigger is proposed. (C) 1999 Elsevier Science B.V. All rights reserved.