Magnetic behavior of new compounds, Gd3RuSn6 and Tb3RuSn6

We report temperature (T) dependence of dc magnetization, electrical resistivity (ρ) and heat-capacity of rare-earth (R) compounds, Gd3RuSn6 and Tb3RuSn6, which are found to crystallize in the Yb3CoSn6-type orthorhombic structure (space group: Cmcm). The results establish that there is an onset of antiferromagnetic ordering near (TN = ) 19 and 25 K respectively. In addition, we find that there is another magnetic transition for both the cases around 14 and 17 K respectively. In the case of the Gd compound, the spin-scattering contribution to ρ is found to increase below about 75 K as the material is cooled towards TN, thereby resulting in a minimum in the plot of ρ(T) unexpected for Gd based systems. Isothermal magnetization at 1.8 K reveals an upward curvature around 50 kOe. Isothermal magnetoresistance plots also show interesting anomalies in the magnetically ordered state. There are sign reversals in the plot of isothermal entropy change versus T in the magnetically ordered state, indicating subtle changes in the spin-orientations with T. The results reveal that these compounds exhibit interesting transport properties.