Periodicity staircase in a Fe/Gd magnetic thin film

TL;DR

This study uncovers a staircase-like periodicity in the stripe domains of an amorphous Fe/Gd magnetic thin film, driven mainly by anisotropy, with experimental and modeling evidence showing quantized jumps in domain periodicity.

Contribution

It reveals a novel staircase structure in magnetic domain periodicity in Fe/Gd thin films and demonstrates that anisotropy, not dipolar interactions, causes this achiral magnetism phenomenon.

Findings

Resonant X-ray scattering shows quantized jumps in stripe periodicity.

Step changes in Q_x are integral multiples of 7 nm, matching the exchange length.

Landau-Lifshitz modeling reproduces the magnetization steps.

Abstract

Presence of multiple competing periodicities may result in a system to go through states with modulated periodicities, an example of which is the self-similar staircase-like structure called the Devil's staircase. Herein we report on a novel staircase structure of domain periodicity in an amorphous and achiral Fe/Gd magnetic thin film wherein the reciprocal space wavevector \textbf{Q} due to the ordered stripe domains does not evolve continuously, rather exhibits a staircase structure. Resonant X-ray scattering experiments show jumps in the periodicity of the stripe domains as a function of an external magnetic field. When resolved in components, the step change along Q$_x$ was found to be an integral multiple of a minimum step height of 7 nm, which resembles closely to the exchange length of the system. Modeling the magnetic texture in the Fe/Gd thin film as an achiral spin arrangement, we have been able to reproduce the steps in the magnetization using a Landau-Lifshitz spin dynamics calculation. Our results indicate that anisotropy and not the dipolar interaction is the dominant cause for the staircase pattern, thereby revealing the effect of achiral magnetism.