Metamagnetic phase transition induces magnetocaloric effect in EuNiGe₃ compound

Full text: In recent decades magnetocaloric effect (MCE) has been attracting great interest motivated by its potential for application in magnetic refrigeration (MR). MR can offer advantages when compared with conventional refrigeration process such as: replacement of polluting gases by solid material and greater efficiency compared to conventional technology. Many efforts have been made to identify promising magnetic materials for application in both room temperature and cryogenics temperatures. The present study aims characterize the magnetic and magnetocaloric properties of EuNiGe₃ compound. Polycrystalline sample was synthesized by arc melting under controlled atmosphere. 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 below 14 K. As magnetic field increase two metamagnetic phase transitions take place at Hc= 20 and 28 kOe and the compound shows ferromagnetic-like behavior. The compound MCE was evaluated through the isothermal magnetic entropy change (-ΔSM) and the relative cooling power (RCP). Negative and positive contributions for –DSM was observed. The maxims values of -ΔSM () and RCP found for EuNiGe₃ compound were, respectively, 7.5 J/kgK and 113.6 J/kg, in ΔH = 50 kOe. These values are comparable to those reported in the literature for other magnetocaloric compounds, in the same temperature range. The obtained results indicate that the EuNiGe3 compound presented interesting characteristics for application in magnetic refrigeration in cryogenic temperatures. 1819. (author)