Effect of Mn-Mn Distance on the Magnetocaloric Properties in Mn x Ge 3 (4.8 ≤ x ≤ 5.15)

Abstract We have systematically investigated the magnetocaloric effect (MCE) of Mn x Ge 3 by tuning the Mn content x (4.8 ≤ x ≤ 5.15). All synthesized polycrystalline samples crystallize in the hexagonal P63/mcm (No.193). The Curie temperature T C increases as x rises from 4.8 to 5.0, remains nearly constant between 5.0 and 5.1, and decreases when x > 5.1. Both the magnetic entropy change (Δ S M ) and refrigeration capacity ( RC ) can be effectively tuned by varying x. The maximum Δ S M reaches approximately 2.42 J kg -1 K -1 at x = 5.05, while the highest RC value is 38.2 J kg -1 at x = 4.8. Based on magnetization and structural analyses, we attribute the variation in MCE to changes in the Mn 2 -Mn 2 interlayer distances, which modulate the magnetic interactions. Which directly influence the magnetic exchange interactions. These results establish a clear correlation between magnetic interactions and magnetocaloric performance in Mn 5 Ge 3 -based compounds, offering valuable insights for tailoring the refrigeration properties of transition-metal germanides.