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

Abstract

Interfacial magnetic coupling, transient thermal response, and carrier and noise levels are investigated for two central aperture detection magnetic super-resolution disks. In one of the disks, the two magnetic layers are exchange-coupled, while in the other the coupling is of magneto-static nature. For the exchange-coupled disk, the coupling between the two magnetic layers 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 coupling depends on the nonuniformity of the magnetization of the storage layer. The readout layer has a square Kerr loop, but its perpendicular magnetization 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 magnetization within the readout layer gives rise to a high level of noise during readout.

Ultrafast Laser Modulation of Local Magnetization Orientation in Perpendicularly Exchange-Coupled Bilayer

“…It is clear that the initial state of magnetization in the probed area is dominated by H, while the direction of magnetization reorientation is controlled by M T , implying that just the exchange field drives the magnetization reorientation after laser excitation. This result agrees with that of the steady measurements for MSR [20], but here we first reveal the dynamics and related timescale.…”

“…Typically, GdFeCo and TbFeCo can be used as the free and pinning layers, respectively, in perpendicular ECCs due to their dissimilar spin-orbit coupling and perpendicular magnetic anisotropy (PMA) [2,19]. RE-TM ECCs have attracted attentions also due to their applied potential in magnetic super resolution (MSR) for magnetooptical readout [20][21][22], but observation of the related dynamical process has not been reported.…”