Successive magnetic transitions and magnetocaloric performances in RE3Co2Ge4 (RE = Gd, Tb and Dy) compounds

The rare earth (RE)-transition metal (TM) based compounds have emerged as one of the best candidates for the application in eco-friendly and effective cooling technology due to their outstanding cryogenic magnetocaloric performances. In this work, three RE-TM germanides RE3Co2Ge4 (RE = Gd, Tb and Dy) were synthesized and characterized, aiming to investigating their structural, magnetic and magnetocaloric properties. These compounds crystallize in the Tb3Co2Ge4-type monoclinic structure (space group C2/m, Z = 2). Two successive ferromagnetic transitions are observed with TC of 31 and 135 K for Gd3Co2Ge4, ferromagnetic and spin reorientation transitions are observed with TC of 24 K and Ts of 19 K for Dy3Co2Ge4, all of which are second ordered. In contrast, Tb3Co2Ge4 exhibits a second order antiferromagnetic transition with TN of 36 K, accompanied with a spin reorientation transition with Ts of 17 K. Furthermore, the ferromagnetic ground state for Gd3Co2Ge4 is also confirmed by the first-principles calculations. Significant cryogenic magnetocaloric performances are observed in these compounds. The determined maximum magnetic entropy change () under a magnetic field change (ΔH) of 0–7 T are 10.7, 5.3 and 11.6 J/(kg·K) for Gd3Co2Ge4, Tb3Co2Ge4 and Dy3Co2Ge4, respectively. Our results suggest that Gd3Co2Ge4 and Dy3Co2Ge4 compounds are attractive candidates for cryogenic magnetic refrigeration applications.