Chiral asymmetry detected in a 2D array of permalloy square nanomagnets using circularly polarized X ray Resonant Magnetic Scattering

TL;DR

This study demonstrates the use of circularly polarized X-ray resonant magnetic scattering to detect chiral asymmetry in a 2D array of permalloy nanomagnets, revealing vortex chiralities and their magnetic interactions.

Contribution

First demonstration of CXRMS sensitivity to chiral asymmetry in a nanomagnet array, linking vortex chirality with magnetic scattering interference.

Findings

Asymmetric magnetic scattering intensity indicates chiral vortex distribution.

Inversion of asymmetry sign with magnetic field reversal confirms chiral sensitivity.

Magnetic interactions between vortices are anisotropic and field-dependent.

Abstract

The sensitivity of Circularly polarized X ray Resonant Magnetic Scattering (CXRMS) to chiral asymmetry has been demonstrated. The study was performed on a 2D array of Permalloy (Py) square nanomagnets of 700 nm lateral size arranged in a chess lattice of 1000 nm lattice parameter. Previous X ray Magnetic Circular Dichroism Photoemission Electron microscopy (XMCD-PEEM) images on this sample showed the formation of vortices at remanence and a preference in their chiral state. The magnetic hysteresis loops of the array along the diagonal axis of the squares indicate a non-negligible and anisotropic interaction between vortices. The intensity of the magnetic scattering using circularly polarized light along one of the diagonal axes of the square magnets becomes asymmetric in intensity in the direction transversal to the incident plane at fields where the vortex states are formed. The asymmetry sign is inverted when the direction of the applied magnetic field is inverted. The result is the expected in the presence of an unbalanced chiral distribution. The effect is observed by CXRMS due to the interference between the charge scattering and the magnetic scattering.