Crystal structure of new R₂TAl₄Ge₂ (R = Y, Gd–Er, T = Fe, Co) quaternary compounds and magnetic properties of Gd₂TAl₄Ge₂

Highlights: • New R₂TAl₄Ge₂ (R = Y, Gd–Er, T = Fe, Co) quaternary compounds was detected. • The R₂TAl₄Ge₂ crystallized in the Tb₂NiAl₄Ge₂-type structure with space group I4/mmm. • The structure of Gd₂TAl₄Ge₂ (T = Fe, Co) was successfully refined by Rietveld method. • The effective magnetic moments of Gd₂CoAl₄Ge₂ and Gd₂FeAl₄Ge₂ were μ_eff = 8.10μ_B and μ_eff = 8.27μ_B. - Abstract: The new R₂TAl₄Ge₂ (R = Y, Gd–Er, T = Fe, Co) quaternary compounds have been synthesized and studied by powder XRD, SEM and MPMS techniques. It is found that the R₂TAl₄Ge₂ compounds crystallized in the tetragonal Tb₂NiAl₄Ge₂-type structure with space group I4/mmm (No. 139). The crystal structures of Gd₂CoAl₄Ge₂ and Gd₂FeAl₄Ge₂ were successfully refined by using Rietveld method. The magnetic measurements of Gd₂CoAl₄Ge₂ and Gd₂FeAl₄Ge₂ show antiferromagnetic ordering at lower temperature. The susceptibilities of Gd₂CoAl₄Ge₂ and Gd₂FeAl₄Ge₂ are followed perfectly by Curie–Weiss behavior in high temperature region. The magnetic measurement shows that the effective magnetic moment is μ_eff = 8.10μ_B (per Gd atom) and the paramagnetic Curie temperature is θ_p = −31.1 K for Gd₂CoAl₄Ge₂, while the effective magnetic moment of Gd₂FeAl₄Ge₂ is μ_eff = 8.27μ_B (per Gd atom) and the paramagnetic Curie temperature is θ_p = −13.7 K. The isothermal magnetization of Gd₂TAl₄Ge₂ (T = Fe, Co) were also investigated