Electrical transport properties of semimetallic GdXsingle crystals (X=P, As, Sb, and Bi)

The large single crystals of stoichiometric and nonstoichiometric Gd monopnictides GdX (X=P, As, Sb, and Bi) are grown by the mineralization method (for X=P and As) and Bridgman method (for X=Sb and Bi). A systematic investigation of the transport properties of GdX single crystals is presented. We report on measurements of the electric resistivity {ρ}(T), magnetoresistance {ρ}(H), and Hall effect performed on the stoichiometric and nonstoichiometric samples at temperatures between 1.6 and 300 K in magnetic fields up to 10 T. The stoichiometric samples behaved as the well-compensated semimetals that order antiferromagnetically at N\'eel temperatures TN=15.9 K for GdP, 18.7 K for GdAs, 23.4 K for GdSb, and 25.8 K for GdBi. The transverse magnetoresistance measured at low temperature follows a {ρ}(H){∝}H² law, and a larger positive ratio MRR=[{ρ}(H)-{ρ}(0)]/{ρ}(0) is observed at 10 T for the four stoichiometric samples. The temperature dependence of the resistivity can be explained by the d-f Coulomb exchange interaction at lower temperatures. The Hall-effect measurements yield a carrier concentration n=2.1×{}10²⁰ cm^-3 for GdAs and n=4.2×{}10²⁰ cm^-3 for GdSb, which are in a good agreement with the de Haas--van Alphen effect measurements. The nonstoichiometric samples showed some anomalies that could be explained qualitatively by the model of trapped magnetic polaron. {} 1996 The American Physical Society.