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 auste nitic stainless steel, is proposed. The transformation from austenite to ma rtensite occurs due to tribological stresses, such as indentation and slidi ng, has the potential to induce phase transformation which in turn generate s a locally ferro-magnetized surface. Surface observations were made using magnetic force sensing systems having a sensing mechanism similar to that o f magnetic force microscope (MFM). Two-dimensional distribution of the magn etic force measured by the sensing systems showed many possible application s in magnetic recording, and magnetic field freezing, etc. Scratching exper iments with a load of 0.4 mN verified the possibility of the material's app lication as a recording media with spatial resolution of submicrometer. Mem orizing phenomena of magnetic field in a stainless steel plate was also obs erved. After a uniform tensile stress generated the phase transformation of a stainless steel thin plate in a magnetic field, the magnetic force distr ibution on the steel surface was measured. The distribution was similar to that of the magnetic field which was induced by an exciting coil. The resul ts indicated that information about the external magnetic field distributio n 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 exte rnal force trigger is proposed. (C) 1999 Elsevier Science B.V. All rights r eserved.