Around the composition Gd4Co3: Structural, magnetic and magnetocaloric properties of Gd6Co4.85(2)

Investigation of the Gd–Co system around the composition Gd4Co3 showed that this compound does not exist. When samples with the nominal composition Gd4Co3 are synthesized a mixture of Gd12Co7 and Gd6Co4.85(2) (=Gd4Co3.23(2)) is observed. Gd6Co4.85(2) is the only compound found around the composition Gd:Co = 4:3. Its structure was determined by means of X-ray diffraction on single crystal with the space group P63/m. The cell parameters are a = 11.593(2) Å and c = 4.0495(14) Å. Its structure is closely related to the Ho4Co3.07-type or to the Ce6Ni1.67Si3-type structure. Gd6Co4.85(2) exhibits only one ferro(ferri)magnetic transition at 219(1) K and the second magnetic transition at 163 K, wrongly attributed to a spin reorientation, corresponds indeed to the ferromagnetic transition of the impurity Gd12Co7. Gd6Co4.85(2) presents magnetocaloric properties with a maximal adiabatic temperature change ΔTad equal to 4.4 K for μ0ΔH = 4.5 T.