Abstract: A magnetic disk device including: one or more disk-shaped magnetic disks; a spindle motor; a magnetic head; an arm for supporting the magnetic head; an enclosure base for housing the above components; an adjacent facing surface which lies in the enclosure base adjacent to the magnetic disk; a non-adjacent facing surface which lies in the enclosure opposite the magnetic disk and is further from the magnetic disk than the adjacent facing surface; a connecting surface for connecting the adjacent facing surface and the non-adjacent facing surface; and a groove which extends in the circumferential direction of the magnetic disk on the magnetic disk inner circumferential side of the adjacent facing surface, wherein one end of the groove is exposed at the connecting surface, while the other end has an end face which is perpendicular to the direction of rotation of the magnetic disk.

Abstract: A recording medium includes at least one recording layer on which information is recorded by multi-photon absorption, and a servo layer disposed in a laminated direction with respect to the recording layer and having a track for guiding a beam spot of laser light having a first wavelength and a beam spot of laser light having a second wavelength along a scanning trajectory. The servo layer and the at least one recording layer constitute a set of layers, and a plurality of sets of layers is formed in the laminated direction. The servo layer is made of a material having a high reflectance with respect to laser light having a third wavelength for generating a servo signal, and low reflectances with respect to the laser light having the first wavelength and the laser light having the second wavelength.