Thermomagnetic recording behavior in the NdTbDyFeCo/DyFeCo-ultrathin bilayer

Thermomagnetic recording behavior was investigated in a bilayer which was composed of a TM-rich NdTbDyFeCo layer and a high-Tc RE-rich DyFeCo ultrathin layer. The magnetic field sensitivity of the bilayer was investigated by a magnetic field modulation method at a low field of 4 kA/m. Carrier-to-noise-ratio depends sensitively on the thickness of the ultrathin layer and reaches its maximum value at approximately 2.5 nm. Using a polarized light microscope it was observed that the domain formation process makes a transition from nucleation-dominated (ND) to wall-motion-dominated (WMD) as the thickness increases, and during the transition the highest magnetic field sensitivity was achieved. We explained those results with a model in which the domain formation started in WMD and ended in ND.<
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