DyPO4: A Three-Dimensional Ising Antiferromagnet

Abstract

The magnetic susceptibility, heat capacity, and optical-absorption spectrum of Dy P${\mathrm{O}}_4$ have been measured as a function of temperature and magnetic field. The optical-absorption spectrum indicates that the magnetic interactions in Dy P${\mathrm{O}}_4$ have the form of the Ising interaction and occur primarily between nearest neighbors. The magnetic-susceptibility and heat-capacity measurements have been compared with exact series expansions for a diamond lattice assuming an Ising system with nearest-neighbor interactions. The theoretical calculations are in agreement with the measurements. The nature of the divergence of the heat capacity at the critical point is examined. Our data do not permit us to distinguish between the applicability of the logarithmic and power-law divergencies since they are indistinguishable in the region of our measurements. The temperature dependence of the critical field for the metamagnetic phase transition has also been determined and compared with the calculated value for the critical field at 0 K obtained from the spectroscopic measurements.