Coexistence of conventional and inverse magnetocaloric effects in terbium substituted Dy2Co3Ge5 compound

In this work, the structural, magnetic, and magnetocaloric properties of the (Tb x Dy 1-x ) 2 Co 3 Ge 5 series (x = 0.3, 0.6, 0.9) are investigated in detail to examine the influence of terbium substitution in Dy 2 Co 3 Ge 5 . Irrespective of Tb concentration, all compounds are found to crystallize in the Lu 2 Co 3 Si 5 -type structure. There is a systematic increase in lattice parameters observed with increasing Tb content. Across the series, an antiferromagnetic ground state with three successive magnetic transitions is observed, consistent with the behavior of the parent compounds. With increasing Tb concentration, the commensurate antiferromagnetic transitions at T 1 and T 2 shift to lower temperatures and exhibit anomalous G -factor dependence, whereas the incommensurate transition at T 3 is weakly affected. These observations highlight the significant role of crystalline electric field effects in addition to the RKKY interaction in governing the magnetic behavior. Furthermore, terbium substitution in the present germanides enhances the antiferromagnetic interactions and reduces the temperature range of short-range ferromagnetic correlations in the paramagnetic state. On the other hand, metamagnetic transitions are found to be a common feature throughout the series. With higher terbium content, the inverse magnetocaloric effect is enhanced, whereas the conventional magnetocaloric effect is suppressed, resulting in nearly equal contributions for x = 0.6. Moreover, estimations of the magnetocaloric properties from magnetization and heat capacity measurements confirm that the inverse magnetocaloric effect observed in this series is genuine and intrinsically associated with the antiferromagnetic ground state.