Study on magnetic domain wall roughness in ferrimagnetic CoGd thin film

Abstract

Magnetic domain wall (DW) motion has long been a subject of research in spintronics field because of its fundamental interest as well as technological applications. When the magnetic DW is driven by a weak magnetic field at finite temperature, the motion is generally occurred by successive thermal activation process, which we call DW creep motion. In this creep regime, the DW can be considered as an elastic string which has finite roughness due to the quenched disorders. As the roughness governs the scaling law of DW speed, it is highly important to determine the roughness in disordered media. In this study, we investigate the roughness of magnetic DW in two different magnetic systems: ferromagnetic Co/Pt and ferrimagnetic GdCo, both are made by sputtering method. By developing a program that can automatically analyze the DW roughness from the obtained DW image, we analyze the DW roughness of Co/Pt and GdCo thin films. The results show that the wandering exponent is similar in two different magnetic systems. This suggests that the DW roughness does not much depend on the magnetic properties, but depend on the fabrication conditions.