Dependence of magnetic domain patterns on plasma-induced differential oxidation of CoPd thin films

TL;DR

This study investigates how plasma-induced differential oxidation affects magnetic domain patterns in CoPd thin films, revealing that oxidation processes can reversibly alter magnetic properties and enable advanced magnetic-domain engineering.

Contribution

It demonstrates the influence of plasma-induced oxidation on magnetic domain evolution and introduces oxidation as a new tool for magnetic-domain engineering.

Findings

Oxidation causes significant changes in magnetic anisotropy energies.

Pre-exposure to plasma can decrease coercive fields by about 10 Oe.

Longer oxidation can reverse the coercive field differences, enabling pattern control.

Abstract

We demonstrate the evolution of the micro-patterned magnetic domains in CoPd thin films pretreated with e-beam lithography and O2 plasma. During the days-long oxidation, significantly different behaviors of the patterned magnetic domains under magnetization reversal are observed via magneto-optic Kerr effect microscopy on different days. The evolution of the magnetic behaviors indicate critical changes in the local magnetic anisotropy energies due to the Co oxides that evolve into different oxide forms, which are characterized by micro-area X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. The coercive field of the area pre-exposed to plasma can decrease to a value 10 Oe smaller than that unexposed to plasma, whereas after a longer duration of oxidation the coercive field can instead become larger in the area pre-exposed to plasma than that unexposed, leading to an opposite magnetic pattern. Various forms of oxidation can therefore provide an additional dimension for magnetic-domain engineering to the current conventional lithographies.