FDTD Readout Analysis of a Near-Field Patterned Media Magneto-Optical Recording System

Recently, a lot of investigation into the use of patterned media for high density magnetic recording has been carried out . Using this system, single bits of data are stored within lithographically defined islands, which are both uniform and discrete in nature, and which enclose a single domain. A combination of the Pseudo Vector Diffraction (PVD) equation and a Finite-Difference Time-Domain (FDTD) method solution of Maxwell´s equations is used to simulate the signals detected at the system output. Due to computational restrictions, the experimentally measured refractive index of the entire Co/Pt stack was utilized instead of the refractive indices of the individual layers.The signals demonstrate that the phase responses of the islands themselves dominate the response contributed by the magnetization state, since the expected polarity reversal between the up and down magnetized states is not observed. The difference in magnitude between the recorded states is very small but is still detectable, and the unmagnetized response lays halfway between.