Ferromagnetic CeSi1.2Ga0.8 alloy: Study on magnetocaloric and thermoelectric properties

We present the magnetic, specific heat, electrical resistivity, and thermoelectric power measurements for the intermetallic compound CeSi1.2Ga0.8. This composition belongs to the series CeSi2-xGax, which exhibits diverse magnetic orderings and different crystallographic structures depending on the substitution level x. It has been previously suggested that for 0.0 < x < 1.3 the compounds crystallize in the α-ThSi2 type structure and for 0.7 < x < 1.3 they order ferromagnetically below 14 K. Our complementary studies for x = 0.8 reveal that it is a complex system due to the Kondo scattering competing with the RKKY interactions. The transition from the paramagnetic to the ferromagnetic state takes place at TC = 12.5(1) K. Moreover, the Seebeck coefficient and electrical resistivity show not only an anomaly related to the magnetic transition, but also a broad maximum at ∼90 K related to the crystal field effect. The case of x = 0.8 is of special interest as it is at the crossing of the characteristic temperatures, i.e. Tord (magnetic ordering temperature) ∼ TK (Kondo temperature) ∼10 K. Additionally, ab initio electronic structure calculations were performed allowing us to determine phase stability, (revealing two stable phases - α-GdSi2-type and α-ThSi2-type structures) as well as spin and orbital moment decomposition on Ce-states for both considered structures.