To prevent falsification of data by arraying plural heated bars with irreversibly changed saturation magnetization in approximately parallel to each other in a recording area of fixed information and coding the fixed information in a frequency modulation system or a phase modulation system in a heated bar arraying pattern or an arraying pattern of nonheated bars existing between every adjacent heated bars.
The plural heated bars 41 formed in an irreversible recording layer 4 by heating this recording layer to be changed irreversibly in saturation magnetization are arrayed in a bar code pattern, where the nonheated bars 42 exist between the adjacent heated bars, thus forming the fixed information recording area. The arrayed pattern of the plural heated bars 41 or the nonheated bars 42 is generated in the FM system or the PM system by coding the fixed information, and whenever information of a magnetic recording layer 3 is rewritten, direct-read-after-write operation takes place in the irreversible recording layer 4. Since even when the information of the magnetic recording layer 3 is falsified, the information of the irreversible recording layer 4 cannot be rewritten, the presence of falsification can be judged by referring to both the layers.
MIMURA SHOHEI (JP)
SHIGETA MASAO (JP)
CHO TSUTOMU (JP)
TDK CORP (JP)