Tuning magnetism through Cu and Cr substitutions in MPS₃ van der Waals magnets

Magnetic van der Waals material MPX₃ (M= metal, X = S or Se) is an intensively studied platform to investigate 2D magnetism. Recent discoveries found that magnetism can persist down the atomic thin layers in some MPX3 compounds. So far, all discovered MPX3 materials display antiferromagnetic order in their ground state. Establishing long-range ferromagnetism has become one important task for the community. Cr-substitution has been found to show a magnetic field-driven polarized ferromagnetism. However, owing to the 3+ valence of Cr ions, substituting the di-valence metal ion in MPX3 is limited to only 10%, which makes it difficult to further explore the potential of this route. Here we report an alternative approach that balances the valence by co-substituting mono-valent metal ions together with the tri-valent Cr ions, through which we were able to replace all M²⁺ to more efficiently tune the magnetism.