Study on magnetic properties and magnetocaloric effect of DyVO4

Abstract

We prepared DyVO4 polycrystal by solid-state reaction. We tested the magnetization of the samples under field cooling and zero field cooling conditions, and analyzed the magnetic phase transition. It was found that Dy3+ had a paramagnetism to antiferromagnetism phase transition near 3.9 K. The isothermal magnetization curve of the sample was drawn under 0–5 T magnetic field, and the maximum magnetic entropy change (−Smmax) under 5 T magnetic field was calculated to be 25.5 J/kg. Interestingly, we found that with the increase of magnetic field, the maximum magnetic entropy change tends to move towards high temperature, which also leads to the relative refrigeration efficiency (RCP) as high as 522 J/kg. We think this may be related to the structural phase transition in the material, which is confirmed by two abnormal peaks on the heat capacity curve. The anomaly near 3 K comes from the antiferromagnetic phase transition of Dy3+, while the anomaly near 13 K comes from the structural phase transition from tetragonal phase to orthorhombic phase. With the increase of the magnetic field, the −ΔSm near the structural phase transition is larger. We calculated the adiabatic temperature change (ΔTad) of the sample by the heat capacity, and showed two peaks near the magnetic phase transition temperature and the structural phase transition temperature, with ΔTadmax of 9.9 K. We use heat capacity curve, Arrott plot and phenomenological universal curve to judge the order of phase transition. Finally, we think that the two phase transitions of the sample are all first order, but the hysteresis loop results show that the hysteresis is very small, which makes DyVO4 have a potential application prospect in magnetic refrigeration materials.