Magnetic recording and reproducing device and magnetic recording and reproducing method

A magnetic recording and reproducing device, comprising:

• a magnetic recording medium;
• and
• a controller configured to control recording and reproduction of information on/from the magnetic recording medium,
• the magnetic recording medium including in sequence a substrate, a storage layer, an exchange layer, and a surface recording layer,
• the storage layer including a first magnetic grain and a first non-magnetic matrix around the first magnetic grain, the first magnetic grain having perpendicular magnetic anisotropy,
• the surface recording layer including a second magnetic grain and a second non-magnetic matrix around the second magnetic grain, the second magnetic grain having perpendicular magnetic anisotropy,
• the first and second magnetic grains having a diameter of 3 nm or more and 20 nm or less,
• the exchange layer including a magnetic metal or a non-magnetic metal and transmitting an exchange interaction between the storage layer and the surface recording layer,
• a coercive force Hcr of the surface recording layer, an exchange field Hexr applied to the surface recording layer, an external magnetic field Har applied to the surface recording layer, a coercive force Hcs of the storage layer, an exchange field Hexs applied to the storage layer, and an external magnetic field Has applied to the storage layer, satisfying following conditions at room temperature,
• Hcr>Hexr+Har
• Hcs>Hexs+Has
• the controller being configured to execute 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.