To get a deeper insight into the magnetic interactions in these materials we carried out firstprinciples DFT calculations. For each compound we relaxed structure, using a primitive two atom cell, and calculated the exchange energies using the broken-symmetry approach . The electronic structure and exchange energies were calculated using a collinear spin-polarised DFT Hamiltonian including a Hubbard U term using CASTEP , including the MBD* disperson correction. We investigated using relativistic noncollinear DFT to prove the noncollinear magnetism found in these vdW MOMs (ESI Sec. S4.5), however these calculations were unable to provide any additional insight, due to the small energy-scales.