Anisotropic behavior of magnetic and transport properties in CePdSb and CePtSb

Measurements of resistivity rho, Hall coefficient R-H, magnetic susceptibility chi, magnetization, specific heat C and magnetoresistance have been performed on the hexagonal ferromagnets CeTSb (T = Pd,Pt) and the isostructural compounds LaTSb using single crystalline samples. Strong anisotropy in rho, rho(c) > rho(a), was observed for both the Ce compounds as well as the La compounds. However, R-H(T) for CeTSb does not exhibit strong anisotropy between H//a and H//c. The anisotropic behavior of chi(T) for the Ce compounds is well reproduced by the crystalline electronic-field model. The analysis of chi(T) suggests that the ferromagnetic exchange interaction along the c axis in CePdSb is much stronger than that in CePtSb. Magnetization measurements reveal that the saturated magnetic moments of 1.32 mu(B) and 0.91 mu(B) for CePdSb and CePtSb lie within the c plane in the ferromagnetic state. The C(T) for CePdSb shows a clear jump at T-C = 17.5 K in addition to a broad peak around 10K. These results suggest that one dimensional magnetic order along the c axis occurs in CePdSb at T-C = 17.5 K and three-dimensional order develops only below 10 K. It is found that rho(c) increases below 8 K and 6 K for CePdSb and CePtSb, respectively, and R-H(H//a; I//c) also increases below 10 K for both compounds. Unlike usual ferromagnets, the transverse and longitudinal magnetoresistances in the ferromagnetic states are largely positive for H//a. These unusual transport properties may be ascribed to the anomalous spin dynamics in the ferromagnetic state of the present systems.