Multiple magnetic states of CoPc molecule on a two-dimensional layer of NbSe$_2$

TL;DR

This study uses ab-initio simulations to reveal that Co-phthalocyanine molecules can exhibit multiple magnetic states when placed on a 2D NbSe2 layer, highlighting complex spin behaviors influenced by correlations and orientation.

Contribution

The paper demonstrates for the first time that CoPc molecules can develop multiple spin states on 2D NbSe2, with detailed analysis of how correlations and orientation affect their magnetic properties.

Findings

CoPc exhibits low, regular, and high spin states on NbSe2.

Correlation effects influence the stability of different spin states.

Molecular orientation impacts the energy hierarchy of magnetic states.

Abstract

Molecular spintronics hinges on the detailed understanding of electronic and magnetic properties of molecules interfaced with various materials. Here we demonstrate with ab-initio simulations that the prototypical Co-phthalocyanine (CoPc) molecule can surprisingly develop multi-spin states once deposited on the two-dimensional 2H-NbSe$_2$ layer. Conventional calculations based on density functional theory (DFT) show the existence of low, regular and high spin states, which reduce to regular and high spins states once correlations are incorporated with a DFT+$U$ approach. Depending on $U$, the ground state is either the low spin or high spin state with energy differences affected by the molecular orientation on top of the substrate. Our results are compared to recent scanning probe measurements and motivate further theoretical and experimental studies on the unveiled rich multi-magnetic behavior of CoPc molecule.