The Gd-Ni-Ga system at 870 ​K as a representative of rare-earth nickel gallides: Crystal structure and magnetic properties

Abstract

The Gd-Ni-Ga system has been investigated at 870 ​K by X-ray and electron microprobe analyses. The known compounds, GdNi3Ga2 (YCo3Ga2-type), Gd3Ni6Ga2 (Ce3Ni6Si2-type), GdNiGa3 (BaNiSn3-type), GdNiGa4 (YNiAl4-type), GdNiGa2 (NdNiGa2-type), Gd2Ni2-2.3Ga1-0.7 (Mo2NiB2-type), GdNiGa (TiNiSi-type), GdNi0.5-0.66Ga1.5-1.34 (CeCu2-type), GdNi0.25Ga1.75 (CaIn2-type) and Gd26Ni9-6.5Ga8-10.5 (Sm26Co11Ga6-type), have been confirmed in this system. New ternaries, ∼GdNi3Ga5 (unknown type), Gd2Ni12.7-9Ga4.3-8 (Th2Zn17-type, R-3m, N 166–2, hP57), GdNi2.2-2Ga2.8-3 (CaCu5-type, P6/mmm, N 191, hP6), Gd2Ni3Ga5 (novel Gd2Ni3Ga5-type, Pnnn, N 48, oP80) and Gd12Ni4.85-5Ga3.15-3 (Er12Ni5Ga3-type, I4/mcm, N 140, tI80), were detected in the Gd-Ni-Ga system. Quasibinary solid solutions were detected for Th2Ni17-type Gd2Ni17, CaCu5-type GdNi5, Ce2Ni7-type Gd2Ni7, CeNi3-type GdNi3, MgCu2-type GdNi2, CrB-type GdNi, AlB2-type GdGa2, Gd3Ga2-type Gd3Ga2 and Cr5B3-type Gd5Ga3 while no appreciable solubility was observed for other binary compounds.Also, new Th2Zn17-type {Nd, Dy, Ho}2Ni9Ga8, Sm2Ni8.5Ga8.5, Tb2Ni9.5-9Ga7.5-8 and Er12Ni5Ga3-type Tb12Ni5Ga3 compounds were synthesized as prolongation of isostructural rows.Gd2Ni9Ga8 is paramagnetic down to 2 ​K GdNiGa2, GdNiGa3 and Gd2Ni3Ga5 are antiferromagnets with the Néel temperatures (TN) of 22 ​K, 14 ​K and 28 ​K, respectively. GdNiGa2 and Gd2Ni3Ga5 show negative and positive magnetic entropy change around TN. GdNi4Ga is a soft ferromagnet with Curie temperature (TC) of 22 ​K and magnetic entropy change of −10.9 ​J/kg⋅K for a field change of 50 ​kOe at TC. Gd12Ni5Ga3 shows ferromagnetic ordering below TC ​= ​140 ​K.