Magnetic and transport properties of the rare-earth-based Heusler phases RPdZ and RPd2Z (Z=Sb,Bi) -: art. no. 094409

Four series of ternary compounds RPdSb (R=Y,Ho,Er), RPdBi (R=Nd,Y,Dy,Ho,Er), RPd2Sb (R=Y,Gd-Er), and RPd2Bi (R=Y,Dy-Er) were studied by means of magnetization, magnetic susceptibility, electrical resistivity, magnetoresistivity, thermoelectric power, and Hall effect measurements, performed in the temperature range 1.5-300 K and in magnetic fields up to 12 T. All these ternaries, except for diamagnetic Y-based phases, exhibit localized magnetism of R3+ ions, and a few of them order antiferromagnetically at low temperatures (T-N=2-14 K). The equiatomic compounds show half-metallic conductivity due to the formation of narrow gaps in their electronic band structures near the Fermi energy. Their Seebeck coefficient at room temperature is exceptionally high (S up to 200 mu V/K), being promising for thermoelectric applications. In contrast, all the 1:2:1 phases are semimetals and their thermoelectric power is much lower (maximum S of 10-25 mu V/K). The Hall effect in the compounds studied corroborates complex character of their electronic structure with multiple electron and hole bands with different temperature and magnetic field variations of carrier concentrations and their mobilities.