Crystal structure of new R2TAl4Ge2 (RÂ =Â Y, Gd-Er, TÂ =Â Fe, Co) quaternary compounds and magnetic properties of Gd2TAl4Ge2

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 μeff = 8.10μB (per Gd atom) and the paramagnetic Curie temperature is θp = −31.1 K for Gd2CoAl4Ge2, while the effective magnetic moment of Gd2FeAl4Ge2 is μeff = 8.27μB (per Gd atom) and the paramagnetic Curie temperature is θp = −13.7 K. The isothermal magnetization of Gd2TAl4Ge2 (T = Fe, Co) were also investigated.