Second Order Magnetic Phase Transition in RCo9Si4 (R = Sm, Gd and Tb)

Magnetization, resistivity and specific heat measurements were performed on the polycrystalline samples of the ternary compounds RCo9Si4 (R = Sm, Gd and Tb) in order to investigate the thermodynamic and transport properties. The low temperature results reveal the onset of ferromagnetic order at Curie temperatures Tc varying between 30 and 50 K for RCo9Si4 on going from Sm to Tb compounds. The electrical resistivities in the ordered state (below TC/2) is in reasonable agreement with the quadratic temperature dependence expected from ferromagnetic spin waves. Thermodynamic and transport data of the ordered ternary compounds reveal a second order phase transition from paramagnetic to the magnetic ordered state which can clearly be derived from the kinks like anomalies in the resistivity data and the jump like anomalies in the specific heat measurements.