Direction-sensitive magnetophotonic surface crystal

TL;DR

This paper presents a magnetophotonic crystal integrating nanosized ferrimagnetic alloys with plasmonic nanoantennas, enabling direction-sensitive optical and magneto-optical control for advanced sensing and switching applications.

Contribution

It demonstrates a novel design combining ferrimagnetic alloys with plasmonic nanoantennas to achieve direction-controlled narrow spectral features in magneto-optical spectra.

Findings

Narrow Fano-type resonance observed and explained by Maxwell simulations.

Magneto-optical spectral features are controlled by magnetic field and light incidence direction.

The structure enables potential high-resolution direction sensors and all-optical magnetization switching.

Abstract

Nanometer-thin rare-earth-transition metal (RE-TM) alloys with precisely controlled compositions and out-of-plane magnetic anisotropy are currently in the focus for ultrafast magnetophotonic applications. However, achieving lateral nanoscale dimensions, crucial for potential device downscaling, while maintaining designable optomagnetic functionality and out-of-plane magnetic anisotropy is extremely challenging. Here we integrate nanosized Tb$_{18}$Co$_{82}$ ferrimagnetic alloys, having strong out-of-plane magnetic anisotropy, within a gold plasmonic nanoantenna array to design micrometer-scale a magnetophotonic crystal that exhibit abrupt and narrow magneto-optical spectral features that are both magnetic field and light incidence direction controlled. The narrow Fano-type resonance arises through the interference of the individual nanoantenna's surface plasmons and a Rayleigh anomaly of the whole nanoantenna array, in both optical and magneto-optical spectra, which we demonstrate and explain using Maxwell-theory simulations. This robust magnetophotonic crystal opens the way for conceptually new high-resolution light incidence direction sensors, as well as for building blocks for plasmon-assisted all-optical magnetization switching in ferrimagnetic RE-TM alloys.