Ordering and interactions in MnPS3

The effect of magnetic dilution, through the production of samples of MnxZn1-xPS3, has been explored experimentally using a SQUID magnetometer and magnetic neutron scattering. The concentration and temperature dependence of the Neel temperature, TN, can be explained by that of the dipolar anisotropy, and these results allow an estimate of the single ion anisotropy. This anisotropy, which is due to the electric field symmetry at the moment site, is found to be significant, and may explain critical neutron scattering results found in the literature. These results show that the critical scattering is of a planar, or XY, universality class rather than an Ising class, although the latter is what would be expected from the zero field, low temperature magnetic order. Also, the change in orientation of the magnetic moments with dilution agrees with a model of competing dipolar and single-ion anisotropies. We conclude that dipole-dipole interactions provide the dominant anisotropy mechanism in MnxZn1-xPS3. In conjunction with exchange and single-site effects, this anisotropy explains much of the observed behaviour