Direct and inverse magnetocaloric effect in antiferromagnetic DyNiGe₃ compound

Full text: In recent years, the magnetic refrigeration (MR), based on magnetocaloric effect (MCE), has attracted attention due to the promise to become an eco-friendly technology with high energy efficiency compared to the conventional gas compression and expansion technology. The MCE is an intrinsic phenomenon of magnetic materials, which manifests as an isothermal magnetic entropy change (- ΔSM) or an adiabatic temperature change (ΔTad) when the material is exposed to a magnetic field change. In order to MR to become reality it is important to characterize new materials searching for promising magnetocaloric properties. Among the different material that have been studied, intermetallic compound that exhibit second order magnetic phase transition is interesting because it can reveal materials with high MCE without hysteresis losses and with a broad temperature range with relevant -values. In the present study polycrystalline sample of DyNiGe₃ was studied in order to characterize it´s magnetocaloric properties. Structural characterizations performed by X-ray diffraction and Rietveld refinement confirmed the desired crystallographic phase. DC magnetization measurement shows a second order antiferromagnetic phase transition around TN = 21 K. External magnetic field induces metamagnetic phase transition around 26.5 kOe. Inverse MCE was observed for ΔH ≤30 kOe. Appreciable values of –DSM (~5,0J/kg.K) over a broad temperature range (18 at 50K) was observed for ΔH = 50 kOe. The obtained results indicate that the DyNiGe₃ compound presented interesting characteristics which are applicable for the low temperature magnetic refrigeration. (author)