Preparation and Properties of a High-Entropy Wolframite-Type Antiferromagnet, (Mn 0.2 Co 0.2 Ni 0.2 Cu 0.2 Cd 0.2 )WO 4 .

The homogeneous high-entropy wolframite-type solid solution (Mn 1/5 Co 1/5 Ni 1/5 Cu 1/5 Cd 1/5 )WO 4 was prepared by solid-state reaction at 1000 °C. Elongated "crystals" were grown from the Na 2 WO 4 flux, but their strongly broadened powder X-ray diffraction patterns indicated partial dissolution. Nevertheless, successive annealing of the homogeneous solid solution for 3-4 h at 800, 700, and 600 °C did not bring any sign of dissolution. Thus, the material is kinetically stable at low temperatures although thermodynamically unstable. The long-range antiferromagnetic order was established at T N ∼ 24.8 K. Based on magnetization and specific heat measurements, a magnetic phase diagram was built, demonstrating the presence of an additional field-induced phase. In contrast to the parent MnWO 4 , no dielectric anomaly has been found down to 2 K.