Europium spin dilution in the ferromagnetic solid solution Eu${}_{4-x}$Ca${}_x$PdMg

The intermetallic compounds Eu${}_4$PdMg and Ca${}_4$PdMg form a complete solid solution Eu${}_{4-x}$Ca${}_x$PdMg. Further phase analytical studies showed that Eu${}_4$PdMg does not allow substitution with strontium. The polycrystalline Eu${}_{4-x}$Ca${}_x$PdMg samples were characterized by powder X-ray diffraction. The structure of Eu${}_{2.233\left(6\right)}$Ca${}_{1.767}$PdMg was refined from single crystal X-ray diffractometer data: Gd${}_4$RhIn type, F$\overline{4}$3m, a = 1,475.42(10) pm, wR2 = 0.0476, 674 F${}^2$ values, 23 variables. Temperature dependent magnetic susceptibility measurements show a drastic decrease of the Curie temperature with increasing calcium substitution. ${}^{151}$Eu Mössbauer spectra of Eu${}_4$PdMg and Eu${}_2$Ca${}_2$PdMg confirm the divalent ground state of europium.