A write-once type information recording medium according to one aspect of the present disclosure includes at least one recording layer. In the information recording medium, the at least one recording layer has a spiral shape in which a land track and a groove track are alternately arranged as a recording track, the recording track is divided into blocks each of which being minimum unit in which recording is performed, and the information recording medium includes a management information area where management information is recorded and a user data area where user data is recorded. Each of the management information areas of both the land track and the groove track on each recording layer of the at least one recording layer is disposed at a same distance from the center of the information recording medium.

On each of a plurality of recording layers of a write-once optical disc, two tracks constituted of adjacent land and groove are formed in a spiral shape. A writing method of data includes: a step of receiving data and a writing instruction of the data; and a step of recording management information, wherein the management information includes: virtual sequential recording range information that manages a last recorded address of the data as a virtual physical sector number; defect list that indicates a replacement correspondence relationship between the virtual physical sector number and an actually recorded physical sector number; and real next writable address information that indicates a real next writable address that is actually recordable subsequently to the physical sector number.

According to one embodiment, a magnetic recording medium includes a first magnetic region, a second magnetic region, a third magnetic region, a fourth magnetic region, and a fifth magnetic region. The second magnetic region is provided between the fifth magnetic region and the first magnetic region in a first direction from the fifth magnetic region to the first magnetic region. The third magnetic region is provided between the fifth magnetic region and the second magnetic region in the first direction. The fourth magnetic region is provided between the fifth magnetic region and the third magnetic region in the first direction. A first composition ratio of a first Pt atomic concentration to a first Co atomic concentration in the first magnetic region is higher than a second composition ratio of a second Pt atomic concentration to a second Co atomic concentration in the second magnetic region.

A magnetic recording and reproducing device according to an embodiment includes a magnetic recording medium and a controller. The magnetic recording medium includes in sequence a substrate, a storage layer, an exchange layer, and a surface recording layer. The controller executes following steps (1) to (6): (1) magnetically recording first information on the surface recording layer; (2) transferring the first information recorded on the surface recording layer to the storage layer; (3) magnetically recording second information on the surface recording layer; (4) magnetically reproducing the second information from the surface recording layer; (5) transferring the first information recorded on the storage layer to the surface recording layer; and (6) magnetically reproducing the first information transferred to the surface recording layer.

A magnetic recording medium includes a rigid substrate, an amorphous soft magnetic underlayer (SUL) on the substrate, a dead magnetic layer on the SUL, a seed layer on the dead magnetic layer, and a magnetic recording layer (MRL) on the seed layer. The dead magnetic layer is configured to provide an interdiffusion region between the amorphous SUL and seed layer with a saturation magnetic moment per unit area less than 510.sup.5 electromagnetic unit (emu)/cm.sup.2, and to produce a recording medium having an increase in tracks per inch (TPI) without significant reduction in bits per inch (BPI), and a net increase in areal density capacity (ADC) relative to a recoding medium that does not have the dead magnetic layer.

A magnetic recording medium includes a rigid substrate, an amorphous soft magnetic underlayer (SUL) on the substrate, a dead magnetic layer on the SUL, a seed layer on the dead magnetic layer, and a magnetic recording layer (MRL) on the seed layer. The dead magnetic layer is configured to provide an interdiffusion region between the amorphous SUL and seed layer with a saturation magnetic moment per unit area less than 510.sup.5 electromagnetic unit (emu)/cm.sup.2, and to produce a recording medium having an increase in tracks per inch (TPI) without significant reduction in bits per inch (BPI), and a net increase in areal density capacity (ADC) relative to a recoding medium that does not have the dead magnetic layer.

On each of a plurality of recording layers of a write-once optical disc, two tracks constituted of adjacent land and groove are formed in a spiral shape. A writing method of data includes: a step of receiving data and a writing instruction of the data; and a step of recording management information, wherein the management information includes: virtual sequential recording range information that manages a last recorded address of the data as a virtual physical sector number; defect list that indicates a replacement correspondence relationship between the virtual physical sector number and an actually recorded physical sector number; and real next writable address information that indicates a real next writable address that is actually recordable subsequently to the physical sector number.

According to one embodiment, a magnetic recording medium includes a first magnetic region, a second magnetic region, a third magnetic region, a fourth magnetic region, and a fifth magnetic region. The second magnetic region is provided between the fifth magnetic region and the first magnetic region in a first direction from the fifth magnetic region to the first magnetic region. The third magnetic region is provided between the fifth magnetic region and the second magnetic region in the first direction. The fourth magnetic region is provided between the fifth magnetic region and the third magnetic region in the first direction. A first composition ratio of a first Pt atomic concentration to a first Co atomic concentration in the first magnetic region is higher than a second composition ratio of a second Pt atomic concentration to a second Co atomic concentration in the second magnetic region.

Write commands in a shingled magnetic recording (SMR) drive are efficiently executed when a write command and associated write data are received by an SMR HDD from a host while the target SMR band for storing the write data is undergoing a refresh operation. In response to the write command, the HDD suspends the refresh operation, stores the write data in nonvolatile memory, and informs the host that the write command has been completed. After the write data are stored in nonvolatile memory, the HDD resumes the refresh operation, and the remaining unrefreshed data in the target SMR band are refreshed by being rewritten to the spare SMR band. The nonvolatile memory can include the spare SMR band in some instances, the target SMR band in some instances, and in both the spare SMR band and the target SMR band in some instances.