Dipolar anisotropy in quasi-2D honeycomb antiferromagnet MnPS3

The nature of the anisotropy in magnetic systems which show isotropic Heisenberg exchange is crucial in determining their magnetic properties. This is particularly true in low-dimensional systems in which the very existence of long-range order depends on the anisotropy. The honeycomb lattice MnPS 3 system has been studied as an example of a magnetically quasi-two-dimensional system of unusual symmetry. In this paper the effect of the dipole-dipole interaction in MnPS 3 on the magnetic ordering is explored through modelling. It is found that the dipolar anisotropy can explain the spin directions both in zero field and above the spin flop phase transition, but it is important that real rather than idealised atomic coordinates are used; this latter consideration is significant because in performing theoretical calculations, it may sometimes be assumed that small deviations away from the ideal can be ignored, but in truth they determine key aspects of the behaviour.