One-dimentional magnonic crystal as a medium with magnetically tunable disorder on a periodical lattice

TL;DR

This study demonstrates that magnonic crystals with tunable magnetic disorder serve as a controllable platform for exploring spin wave excitations, revealing how magnetic history influences collective magnonic states and their responses.

Contribution

It introduces a method to control and study disorder in magnonic crystals through magnetic field variation, linking magnetic ground states to FMR responses.

Findings

Strong correlation between FMR response and magnetic disorder.

Identification of anti-ferromagnetic and ferromagnetic magnonic states.

Magnetic states can be switched by changing magnetization history.

Abstract

We show that periodic magnetic nanostructures (magnonic crystals) represent an ideal system for studying excitations on disordered periodical lattices because of the possibility of controlled variation of the degree of disorder by varying the applied magnetic field. Ferromagnetic resonance (FMR) data collected inside minor hysteresis loops for a periodic array of Permalloy nanowires of alternating width and magnetic force microscopy images of the array taken after running each of these loops were used to establish convincing evidence that there is a strong correlation between the type of FMR response and the degree of disorder of the magnetic ground state. We found two types of dynamic responses: anti-ferromagnetic (AFM) and ferromagnetic (FM), which represent collective spin wave modes or collective magnonic states. Depending on the history of sample magnetization either AFM or FM state is either the fundamental FMR mode or represents a state of a magnetic defect on the artificial crystal. A fundamental state can be transformed into a defect one and vice versa by controlled magnetization of the sample.