Synthesis, structure, magnetism and specific heat of YCrO4 and its zircon-to-scheelite phase transition

The scheelite-type YCrO4 with space group I4(1)/a was synthesized at 6.0 GPa and 450 degrees C from its ambient-pressure zircon-type phase in I4(1)/amd symmetry. Accompanying the structural phase transition from zircon to scheelite, magnetic and specific heat properties are changed drastically. In magnetism, YCrO4 will transform from being ferromagnetic with Curie temperature of about 9 K for the zircon phase to being antiferromagnetic with Neel temperature of 21 K for the scheelite phase. The magnetic superexchange interactions are rather weak due to the poor d-band orbital overlap. Corresponding to the magnetic transition, a lambda-type anomaly in specific heat is observed in the zircon- and scheelite-type YCrO4, respectively. Calculations show that the magnetic entropy changes in experiment are less than those in theory in both of the phases, especially for the scheelite phase.