Higher-order ferromagnetic resonances in periodic arrays of synthetic-antiferromagnet nanodiscs

TL;DR

This paper explores the spin dynamics and higher-order ferromagnetic resonances in synthetic-antiferromagnet nanodisc arrays, demonstrating tunable GHz functionalities through multilayer design and intra-SAF asymmetry control.

Contribution

It introduces a detailed analysis of higher-order ferromagnetic resonances in SAF nanodiscs and shows how intra-SAF asymmetry can be used to control these resonances.

Findings

Three distinct resonance modes at room temperature

Resonance modes collapse into two below the Curie temperature

Micromagnetic simulations accurately recreate experimental spectra

Abstract

We investigate spin dynamics in nanodisc arrays of synthetic-antiferromagnets (SAF) made of Py/NiCu/Py trilayers, where the NiCu spacer undergoes a Curie transition at about 200 K. The observed ferromagnetic resonance spectra have three distinct resonance modes at room temperature, which are fully recreated in our micromagnetic simulations showing also how the intra-SAF asymmetry can be used to create and control the higher-order resonances in the structure. Below the Curie temperature of the spacer, the system effectively transitions into a single-layer nanodisc array with only two resonance modes. Our results show how multi-layering of nano-arrays can add tunable GHz functionality relevant for such rapidly developing fields as magnetic meta-materials, magnonic crystals, arrays of spin-torque oscillators and neuromorphic junctions.