Magnetic and electrical properties of the stannides RE3Co6Sn5 (RE = Sm, Gd, Tb and Dy)

Polycrystalline samples of the ternary intermetallics RE3Co6Sn5 (RE = Sm, Gd, Tb and Dy) were studied by means of magnetization, dc magnetic susceptibility and electrical resistivity measurements. All these stannides were found to order magnetically at low temperatures. Sm3Co6Sn5 is antiferromagnetic below TN = 8 K, while Tb3Co6Sn5 exhibits ferromagnetic ordering below TC = 16 K. The other two compounds show more complex magnetic behaviour with subsequent phase transitions in the ordered regions. For Gd3Co6Sn5 one observes the onset of ferromagnetism at TC = 25 K, which is followed by a change in the magnetic structure at T1 = 12 K. In the case of Dy3Co6Sn5 an antiferromagnetic type of order sets in at TN = 7 K, and then a spin structure rearrangement occurs at T1 = 3 K that yields a ferromagnetic component at lower temperatures. All the ternaries studied exhibit metallic-like conductivity with pronounced anomalies at the magnetic phase transitions. The thermoelectric power, measured for Gd3Co6Sn5, and for comparison also for Y3Co6Sn5 and Er3Co6Sn5, is for each compound negative and of the order of several ?V K?1 at room temperature.