Structures and Magnetic Properties of Europium-Transition Metal-Gallium Ternary Intermetallic Compounds with 1:3 Type

The crystal structures and magnetic properties of novel EuT_rGa_3?r (T=Pd, Ir, Rh) intermetallic compounds are investigated by using powder x-ray diffraction and magnetic measurements. EuT_rGa_3?r crystallizes in orthorhombic structure with space group of Cmcm and Z=4. There are four kinds of nonequivalent 4c crystal positions in EuT_rGa_3?r unit cell, which are occupied by 4Eu, 4Ga^I, 4(Ga^II, T) and 4Ga^III, respectively. EuT_rGa_3?r exhibits the complex magnetic states in low-temperature regime, with the three-, two- and one-antiferromagnetic transitions occurring for T=Ir, T=Rh and T=Pd, respectively. It might be due to the Kondo effect: a localized antiferromagnetic interaction of the isolated impurity spins with the surrounding conduction electrons at low-temperature regime.