CrSBr alloys with tunable optical and magnetic properties an der Waals (vdW) magnets offer a new breath to solid state magnetism by providing an interesting platform to implement spintronic or magnonic schemes with original opportunities in terms of integration into vdW heterostructures. The main reason is the large tunability of the magnetic properties of vdW magnets by external means. Chromium sulfur bromide (CrSBr) is an air-stable layered direct band gap vdW semiconductor with a band gap close to 1.5 eV and strong optical emission that arises from tightly bound excitons at 1.3 eV. Below TN = 132 K, CrSBr is an A-type antiferromagnet (A-AFM) and is the prototype vdW magnet with strong coupling between its magnetic properties and its electronic band structure. Here, we show the existence of mixed-halogen compounds CrSBr1−xClx with optical and magnetic properties tunable with the composition and showing the same peculiar coupling between their electronic band structure and their magnetic ground state. As Br or Cl atoms are located in the outer part of the layers, they lie in the van der Waals gaps and substituting Br with Cl atoms is expected to change the interlayer interaction and the Cr−Cr super-exchange paths. Using low-temperature Raman scattering and optical spectroscopy, we characterize the vibrational properties of the different alloys by the evolution of their phonon spectrum and determine the exciton energies. We show that these alloys are direct band gap semiconductors with a bright photoluminescence close to 1.3 eV, composed of a zero-phonon emission line with lower-energy phonon replicas. Applying an external magnetic field induces changes in the exciton emission energy related to the magnetic state of the Cr ions. We show that the peculiar physics of spin dependent interlayer hopping or localization in CrSBr also exists in these alloys. Both the critical magnetic field values and the single-ion anisotropy decrease upon incorporation of Cl ions. These experiments establish CrSBr1−xClx alloys as CrSBr-like systems with similar magneto-optical effects and with the possibility of tuning their magnetic properties by adjusting the Cl content.
More details in NanoLetters 26, 773, (2026)
Contact: shalini.badola [at] lncmi.cnrs.fr ; clement.faugeras [at] lncmi.cnrs.fr