| 摘要 |
An information memory medium (10) includes disk-shaped substrates (30a, 30b) and recording layers (32a, 32b). It also has a centering member (38a, 38b) whose coefficient of thermal expansion resembles that of the substrates (30a, 30b). Two flat magnetic members (40a, 40b) are situated in annular depressions (68a, 68b) provided in the centering member. The annular depressions are larger than the magnetic members so that differences in thermal expansion can be absorbed.
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