Anisotropic Transport and Magnetic Properties of Charge-Density-Wave Materials RSeTe₂ (R = La, Ce, Pr, Nd)

Single crystals of RSeTe₂ (R = La, Ce, Pr, Nd) are synthesized using LiCl/RbCl flux. Transport and magnetic properties in the directions parallel and perpendicular to the a–c plane are investigated. We find that the resistivity anisotropy ρ_⊥/ρ_|| lies in the range 486–615 for different compounds at 2 K, indicating the highly two-dimensional character. In both the orientations, the charge-density-wave transitions start near T_CDW=284(3) K, 316(3) K, 359(3) K for NdSeTe₂, PrSeTe₂, CeSeTe₂, respectively, with a considerable increase in dc resistivity. While for LaSeTe₂, no obvious resistivity anomaly is observed up to 380 K. The value of T_CDW increases monotonically with the increasing lattice parameters. Below T_CDW, slight anomalies can be observed in NdSeTe₂, PrSeTe₂ and CeSeTe₂ with onset temperature at 193(3) K, 161(3) K, 108(3) K, respectively, decreasing as lattice parameters increase. Magnetic susceptibility measurements show that the valence state of rare earth ions are trivalence in these compounds. Antiferromagnetic-type magnetic order is formed in CeSeTe₂ at 2.1 K, while no magnetic transition is observed in PrSeTe₂ and NdSeTe₂ down to 1.8 K.