Anisotropic transport and magnetic properties and magnetic-polaron-like behavior in CeTe2-x

Highly anisotropic properties of CeTe2-x with the layered Cu2Sb-type struct ure have been found by the measurements of electrical resistivity rho(T), m agnetic susceptibility chi(T) and mag netization M(B) on single crystals fo r x = 0.15-0.18. Both M(B parallel to c) and M(B perpendicular to c) at 2K exhibit a metamagnetic transition at 0.04T. M(B parallel to c) saturates ra pidly to a value of 1.06 mu(B)/f.u. at around B = 0.2 T, whereas M(B perpen dicular to c) gradually increases to a value of 0.75 mu(B)/f.u. at 5.5 T. T he absence of hysteresis and remanence in nl(B) indicates an antiferromagne tic ground state. The resistivity ratio rho(parallel to)c/rho perpendicular to(c) increases from 3 to 150 on cooling from 300 It to 1.5 K(. Both rho(p arallel to)c, and pi, exhibit a sharp peak at 6 K before the onset of long- range magnetic order at T-N = 4.3 K, where chi(T) exhibits a sharp peak. Me asurements of the Hall coefficient R-H(T), specific heat C(T), magnetoresis tance rho(B) and electron tunneling have been done for polycrystals with x = 0.13 and 0.18. Electron-tunneling spectra at 77 K revealed the presence o f a charge density wave with a pseudogap of 0.35 eV. It is found that C(T) exhibits a peak at TN With a significant tail up to 10K, whereas Ra(T) cont inuously increases. The magnetic entropy at TN is only 0.7R In 2, being ind icative of a, short-range order above TN. At 1.5 K, rho(B) shows a peak at 0.075 T and then decreases rapidly for B less than or equal to 1 T, resulti ng in a negative magnetoresistance of 20%. These results are analogous to t hose found in EuTe0.9, GdAs0.95 and CeSb, where low-density carriers form a pseudo-localized state and align the 4f spins within a magnetic polaron.