Reversible memory structure for optical reading and writing and which is capable of erasure

A reversible memory system comprising:

• a substrate having an upper surface;
• a recording metal layer formed on said upper surface and adhering thereto of said substrate and essentially consisting of;
• a recording medium made of an alloy which undergoes martensitic transformation from a first martensitic to a second martensitic phase at a predetermined temperature and which undergoes a stress-induced transformation in a region in which a pressure is applied at a temperature less than or equal to a predetermined characteristic temperature, the region in which the pressure is applied undergoing a transformation from the first to the second phase and which remains adhered and non-deformed to said surface of said substrate in both first and second phases;
• means for generating a pulsed laser beam;
• means for directing the laser beam toward said recording layer in a recording mode, so as to allow the region in said recording layer irradiated with the laser beam to undergo said stress-induced transformation;
• means for converting a portion of said recording layer from the second martensitic phase to the first martensitic phase by a martensitic reverse transformation;
• and
• detecting means for detecting the phase state of the region in said recording layer.