Plasma-induced magnetic patterning of FePd thin films without and with exchange bias

TL;DR

This paper presents a method to control magnetic domain structures in FePd thin films through plasma patterning, enabling precise magnetic engineering for potential data-storage and spintronic applications.

Contribution

It introduces plasma surface patterning as an effective technique to manipulate magnetic properties in FePd thin films, including domain wall pinning and exchange bias effects.

Findings

Magnetic domain walls are pinned by plasma patterning.

Plasma treatment increases the magnetic field needed for reversal.

Competition between uniaxial anisotropy and exchange bias observed.

Abstract

We demonstrate control of magnetic domain structures in continuous FePd thin films by patterning their surfaces with plasma treatment. The Fe-oxide layer formed on the surface upon ambient exposure of the FePd alloy thin film grown on an Al$_2$O$_3$(0001) substrate was patterned into microstructures by e-beam lithography followed by O$_2$- or Ar-plasma treatment. Microscopic pinning of magnetic domain walls in the thin films is then observed by magneto-optic Kerr effect microscopy, with the magnetic field needed to reverse the magnetization of the plasma-treated areas being larger than that for the untreated areas. An intriguing competition between the uniaxial anisotropy and the exchange bias is also observed in the system. This study demonstrates that patterning of the film surface with plasma treatment can be an easy and efficient method for sophisticated engineering of magnetic structures in thin films, and therefore has potential application in developing future data-storage and spintronic devices.