Observation of angle-dependent mode conversion and mode hopping in 2D annular antidot lattice

Nikita Porwal,Jaivardhan Sinha,P K Datta,Koustuv Dutta,Sucheta Mondal,Anjan Barman,Samiran Choudhury,Anulekha De

doi:10.1038/s41598-019-48565-8

Abstract

We report spin-wave excitations in annular antidot lattice fabricated from 15 nm-thin Ni80Fe20 film. The nanodots of 170 nm diameters are embedded in the 350 nm (diameter) antidot lattice to form the annular antidot lattice, which is arranged in a square lattice with edge-to-edge separation of 120 nm. A strong anisotropy in the spin-wave modes are observed with the change in orientation angle (ϕ) of the in-plane bias magnetic field by using Time-resolved Magneto-optic Kerr microscope. A flattened four-fold rotational symmetry, mode hopping and mode conversion leading to mode quenching for three prominent spin-wave modes are observed in this lattice with the variation of the bias field orientation. Micromagnetic simulations enable us to successfully reproduce the measured evolution of frequencies with the orientation of bias magnetic field, as well as to identify the spatial profiles of the modes. The magnetostatic field analysis, suggest the existence of magnetostatic coupling between the dot and antidot in annular antidot sample. Further local excitations of some selective spin-wave modes using numerical simulations showed the anisotropic spin-wave propagation through the lattice.

Highlights

Advancements in lithography techniques have triggered fabrication of artificially patterned magnetic nanostructures, which have potential applications in high density magnetic storage[1], memory[2], logic[3], transistor[4], while strongly coupled magnetic nanowires, nanodots and magnetic antidot lattices have potential applications in on-chip data communication and processing devices
The annular antidot lattice is a two-dimensional (2D) binary magnonic crystal in the form of embedded nanodots in a periodic Ni80Fe20 antidot lattice arranged in square symmetry
The atomic force microscope (AFM) and magnetic force microscope (MFM) images of the sample are presented in ref.[32]

Summary

Introduction

Advancements in lithography techniques have triggered fabrication of artificially patterned magnetic nanostructures, which have potential applications in high density magnetic storage[1], memory[2], logic[3], transistor[4], while strongly coupled magnetic nanowires, nanodots and magnetic antidot lattices have potential applications in on-chip data communication and processing devices The latter, known as magnonic crystal (MC), the magnetic analogue of electronic, photonic and phononic crystals, have strongly emerged during last one decade and extensive research have been carried out on ferromagnetic nanowire arrays[5], dot arrays[6,7,8,9,10] and antidot arrays[11] to that end. We believe that our findings could be important in the contest of the present efforts to understand the SW dynamics in the emerging field of binary magnonic crystals

Methods

Results

Conclusion