Origin of magnetic switching field distribution in bit patterned media based on pre-patterned substrates

Abstract

Using a combination of synchrotron radiation based magnetic imaging and high-resolution transmission electron microscopy we reveal systematic correlations between the magnetic switching field and the internal nanoscale structure of individual islands in bit patterned media fabricated by Co/Pd-multilayer deposition onto pre-patterned substrates. We find that misaligned grains at the island periphery are a common feature independent of the island switching field, while irregular island shapes and misaligned grains specifically extending into the center of an island are systematically correlated with a reduced island reversal field.

Influence of stray fields on the switching-field distribution for bit-patterned media based on pre-patterned substrates

“…The elevation distance between islands and trenches is given by the height of the substrate pillars. Our modeling does not take into account the deviation of the island shape from the perfect prism as observed by transmission electron micrographs of our BPM islands 4 and in other pre-pattern substrate-based BPM. 13,15 Furthermore, our assumption neglects any deposition shadowing effect in the trenches which becomes increasingly important at higher filling factors, i.e., when the ratio between the island height and the trench width becomes larger.…”

“…Island-to-island perpendicular-anisotropy variation, especially presence or absence of nucleation (trigger) crystalline grains with a lower-than-average anisotropy, has been found to be the main origin of intrinsic SFD. [3][4][5] In the present work, we investigate the influence of the stray fields on the island reversal. [6][7][8][9][10] Even though long strings of identical up or down bits are usually forbidden to reduce demagnetization effects and ensure proper timing of bit read out, the design of BPM requires an effective understanding and meaningful modeling of these effects.…”

“…The error bars of the experimental data points (open circles) account for the statistical error due to the limited ensemble size in the FOV. 4 The solid lines are fits to the experimental data points. The filled curves show the SFDs calculated from these fits.…”

“…Further details about the sample preparation and the imaging experiment can be found in our previous publication. 4 In the experiments presented here, we imaged the system at different states in the magnetic hysteresis loop. In total, we have recorded 60 images for each FOV at 22 different field values within 10 hysteresis cycles always starting from saturation at À7.1 kOe.…”

X-ray holography with a customizable reference

“…The technique is particularly suited to imaging magnetic domains and other magnetic samples because holograms generated with circularly polarized X-rays can be used to separate charge scattering from magnetic scattering [3][4][5] . X-ray holography has developed into a powerful single measurement technique 1,6 and has promising applications using X-ray lasers to study structures of radiation-sensitive samples and the structural changes of transient phenomena [6][7][8] .…”