Noise and coupling in magnetic super-resolution media for magneto-optical readout

Interfacial magnetic coupling, transient thermal response, and carrier and noise levels are investigated for two central aperture detection magnetic s uper-resolution disks. In one of the disks, the two magnetic layers are exc hange-coupled, while in the other the coupling is of magneto-static nature. For the exchange-coupled disk, the coupling between the two magnetic layer s is fairly strong, and the Kerr loop of the readout layer does not have a square shape. For the magneto-statically coupled disk, the strength of coup ling depends on the nonuniformity of the magnetization of the storage layer . The readout layer has a square Kerr loop, but its perpendicular magnetiza tion in the hot region under the focused spot has random orientation if the stray field from the storage layer is weak. This random orientation of mag netization within the readout layer gives rise to a high level of noise dur ing readout. (C) 1999 American Institute of Physics. [S0021-8979(99)04209-7 ].