Coloring problem and magnetocaloric effect of Gd3Co2.2Si1.8

The Gd3Co2.2Si1.8 compound was synthesized by arc melting the constituent elements and subsequent annealing at 1070 K for 120 h. It adopts the Dy3Co2.2Si1.8-type structure with the space group Cmcm and the unit cell parameters of a = 4.1176(7) Å, b = 10.305(2) Å, c = 12.778(2) Å and V = 542.2(2) Å3. The Co and Si atoms preferentially occupy the 8f and 4a/4c sites, respectively. The atomic electronegativity and electron density at a given site determine its site occupation, according to the analysis of the electronic structure. Gd3Co2.2Si1.8 orders ferromagnetically with the Curie temperature of 172 K. The isothermal magnetic entropy change, −ΔSm, reaches the maximum value of 7.09 J/kg K at 170 K for a field change of 0–50 kOe.

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► Gd3Co2.2Si1.8 adopts the Er3Ge4 structure (space group Cmcm).
► Si and Co show site preference.
► The electronic factors determine the site occupation of Si and Co.
► Gd3Co2.2Si1.8 order ferromagnetically below 172 K.