Discovery of a large unquenched orbital moment in a 2D van der Waals ferromagnet

The existence of the V³⁺-ion orbital moment in the van der Waals ferromagnet VI₃ is still an open issue. The huge magnetocrystalline anisotropy in conjunction with the significantly reduced ordered magnetic moment compared to the spin-only value provides strong but indirect evidence of a large V orbital moment. Despite of that, some experimental and theoretical works still indicate a quenched orbital moment. The size of the orbital moment is related to the symmetry and ground state of VI₃, and therefore in order to understand and model this system it is important to solve this open question.

In our work we have used the unique capability of x-ray magnetic circular dichroism to determine the orbital component of the magnetic moment. Our results provide a direct proof of an exceptionally sizable orbital moment of the V³⁺ ion in VI₃. Moreover, we have employed ligand field multiplet simulations of the XMCD spectra. Our simulations where done in synergy with results from DFT calculations. The simulations agree with the existence of two V sites with different orbital occupations and magnitudes of the orbital moment in the ground state. Our results give an important piece of information in the understanding of the exotic properties of this system.

In our work we have used the unique capability of x-ray magnetic circular dichroism to determine the orbital component of the magnetic moment. Our results provide a direct proof of an exceptionally sizable orbital moment of the V³⁺ ion in VI₃. Moreover, we have employed ligand field multiplet simulations of the XMCD spectra. Our simulations where done in synergy with results from DFT calculations. The simulations agree with the existence of two V sites with different orbital occupations with different magnitudes of the orbital moment in the ground state. Our results solve the open debate and give an important piece of information in the understanding of the exotic properties of this system. It also shows that the existence of an unquenched orbital moment can be more general in other 2D van der Waals systems exhibiting high magnetic anisotropy.