Substrate-induced spin reorientation in a chromocene single-molecule magnet

Controlling the spin orientation of magnetic systems is crucial for various quantum technologies. In this work, applying first-principle studies, we have investigated how interfacial interactions between a single-molecule magnet (SMM), chromocene $({\mathrm{CrCp}}_{2})$, and substrates (magnetic and nonmagnetic) could control the magnetization of the SMM. Due to magnetic anisotropy, an isolated chromocene molecule exhibits the magnetization direction aligned parallel to the principal molecular axis. Typically, molecule-substrate interactions quench the magnetic anisotropy in the SMMs. In the current work, we observed a switch in the magnetization direction from out-of-plane to in-plane direction while ${\mathrm{CrCp}}_{2}$ is deposited on Au(111), graphene, hexagonal closed packed--Co(0001) and face-centered cubic--Co(111) substrates. The resulting interface formations induce structural and electronic structure changes in the SMMs. We realized that only the structural change enhanced the SMM behaviors of ${\mathrm{CrCp}}_{2}$ compared to the isolated systems. Unfortunately, this is inseparable from the electronic structural changes at the interface. The charge density redistribution at the interfaced molecule modulates the magnetic anisotropy of SMMs and switches their magnetization directions. Finally, we explored the complex nature of the magnetic interactions between the SMM and magnetic substrate, accounting for the Dzyaloshinski-Moriya and symmetric/antisymmetric exchange interactions.