The Ce-Ni-Ga system at 670/870 K: magnetic properties and heat capacity of ternary compounds

Abstract The Ce-Ni-Ga system has been investigated at 670/870 K by X-ray and electron microprobe analyses. The known compounds, i.e. CeNi9Ga4 and CeNi5.7Ga7.3 (LaCo9Si4-type), CeNi7Ga6 (LaNi7In6-type), CeNi6.5-6.15Ga6.5-6.85 (Ce2Ni13Ga13-type), CeNi3-3.2Ga2-1.8 (YCo3Ga2-type), CeNi1-1.2Ga3-2.8 (CePtGa3-type), CeNiGa (ZrNiAl-type), CeNiGa2 (NdNiGa2-type), Ce2Ni2-2.06Ga1-0.94 (Mo2NiB2-type) and Ce3Ni2Ga2 (La3Ni2Ga2-type), have been confirmed in this system at 870 K. A new ter nary Ce2Ni6Ga (Er2Co7-type, R-3m, N 166-2, hP54) was detected at 870 K and ∼Ce5Ni2Ga (unknown type structure) was identified at 670 K in this system. Quasibinary solid solutions were detected at 870 K for CeNi5, CeNi3 and CeGa2 while no appreciable solubility was observed for other binary compounds of the Ce-Ni-Ga system. CeNi6.5Ga6.5, CeNi7Ga6 and CeNi9Ga4 are Curie-Weiss paramagnets down to 2 K, exhibiting magnetic-field-induced ferromagnetism and field-enhanced heat capacity at low temperatures. CeNiGa2, CeNiGa3 and Ce5Ni2Ga are antiferromagntics with the Neel temperatures at 4-6 K and Curie-Weiss paramagnetics at high temperatures. CeNi3Ga2, CeNiGa and Ce2Ni2Ga show temperature insensitive paramagnetism at high temperatures and Curie-Weiss paramagnetism at low temperature, suggesting a mixed valence state of Ce(III) and Ce(IV).