Crystal structure and magnetic properties of GdSi1.78, Gd(Si0.684Ge0.316)1.78, GdGe1.57, and GdSn2 compounds

• The off-stoichiometry features and multiple phase transitions are studied in detail.
• All compounds are antiferromagnetic ordering.
• The results are beneficial to understand the off-stoichiometric compounds.

Intermetallic compounds of Gd with Si, Ge, and Sn near 1:2 stoichiometry adopt several closely related crystal structures. We find that GdSi1.78 and Gd(Si0.684Ge0.316)1.78 crystallize in the same GdSi1.4-type orthorhombic structure (space group Imma), while GdGe1.57 and GdSn2 adopt α-ThSi2-type tetragonal structure (space group I41/amd) and ZrSi2-type orthorhombic structure (space group Cmcm), respectively. All compounds order antiferromagnetically; their Néel temperatures are only weakly affected by the magnetic field of less than 50 kOe. Unusual features are observed including multiple phase transitions and thermomagnetic irreversibilities.