A tale of two polymorphs-growth and characterization of α-LnNiGa 4 (Ln = Y, Gd-Yb) and β-LnNi1-xGa4 (Ln = Tb-Er)
The single crystals of two polymorphs of LnNiGa4, namely, the orthorhombic α-LnNiGa4 (Ln = Y, Gd-Yb) and, a new polymorph, the tetragonal β-LnNi1-xGa4 (Ln = Tb-Er), were successfully grown by using the self-flux method. α-LnNiGa4 (Ln = Y, Gd-Yb) is isostructural to YNiAl4 and can be described as an edge-sharing polyhedral of Ni@Ga7Ln2 (Ln = Y, Gd-Yb) along the ac-plane that is sandwiched between the square nets of the Ga atoms along the b-axis. The structure of β-LnNi1-xGa4 (Ln = Tb-Er) is a distorted variant of the Ce2NiGa10-structure type with a Ni deficiency and multiple Ga split positions and is structurally related to YNiGa3Ge. The magnetic data for β-LnNi 1-xGa4 (Ln = Tb-Er) and the transport properties for α-LnNiGa4 (Ln = Y, Gd-Tm) and β-LnNi1-xGa 4 (Ln = Tb-Er) are reported. Antiferromagnetic correlations are observed in the magnetic susceptibility of β-LnNi1-xGa 4 (Ln = Tb-Er), where the magnetic transitions occurred below 7 K and with effective moments that are consistent with free Ln3+ ions. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.