Switchable Magnonic Crystals Based on Spin Crossover/CrSBr Heterostructures

TL;DR

This paper presents a novel hybrid 2D heterostructure combining spin-crossover molecules with CrSBr to create tunable magnonic crystals that can be dynamically controlled using light-induced spin state switching.

Contribution

It introduces a chemically engineered, switchable magnonic crystal platform by integrating SCO molecules with 2D magnets, enabling dynamic control of spin wave propagation.

Findings

Fe-pz molecules are stable on CrSBr and preserve SCO bistability.

Patterned Fe-pz creates magnonic crystals that filter spin waves.

LIESST induces reversible strain, reshaping magnonic band structure.

Abstract

The progress of magnonics ultimately depends on material platforms that offer precise control of spin waves propagation. Here, we put forward a chemical strategy to create locally tunable magnonic crystals by integrating switchable spin-crossover (SCO) molecules with 2D van der Waals magnets. Specifically, we investigate from first principles a hybrid molecular/2D heterostructure formed by [Fe((3,5-(CH3)2Pz)3BH)2] molecules (Fe-pz) deposited on a single-layer of semiconducting CrSBr. We show that Fe-pz molecules are stable on CrSBr while preserving its SCO bistability, particularly in densely packed molecular arrays. By patterning Fe-pz into periodic stripes separated by pristine CrSBr regions, the interface becomes a magnonic crystal that filters spin waves at selected frequencies. Crucially, light-driven excited spin-state trapping (LIESST) enables LS-HS switching and induces up to ~1.3% local strain in CrSBr, which in turn reshapes the magnonic band structure in a dynamic and reversible manner. These results establish Fe-pz@CrSBr as a switchable platform for on-chip, programmable magnonic devices.