| 摘要 |
PURPOSE:To use an inexpensive material for a recording layer and to reduce cost by providing the recording layer of a material of which the magnetic permeability changed with phase transformation on a base plate consisting of a permanent magnet material. CONSTITUTION:A recording layer 3 is provided on a base plate 1 by using a a material of which the magnetic permeability changes with phase transformation. There is stainless steel of an austenite type having the compsn. range where induced martensite is generated by work strain as the material of which the magnetic permeability changes with the phase transformation. The state of the austenite material with the standard compsn. consisting of 18% Cr-18% Ni has about magnetic permeability mu=1.02 and is nearly non-magnetic but is the material is heated and quickly cooled, the material has the martensite compsn. and magnetism. If the material is therefore heated by using layer light 4, the heated part 5 is quickly cooled after the heating and is made into martensite. The magnetic permeability concentrates is made into martensite. The magnetic permeability concentrates only in this part and the magnetic flux increases. The increase in the magnetic density is detected and is read as a signal. |
