Abstract
Measurements of resistivity ρ, Hall coefficient RH, magnetic susceptibility χ, 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 ρ, ρ c>ρ a, was observed for both the Ce compounds as well as the La compounds. However, RH(T) for CeTSb does not exhibit strong anisotropy between H//a and H//c. The anisotropic behavior of χ (T) for the Ce compounds is well reproduced by the crystalline electronic-field model. The analysis of χ (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, μ B and 0.91, μ B for CePdSb and CePtSb lie within the c plane in the ferromagnetic state. The C(T) for CePdSb shows a clear jump at TC=17.5, K in addition to a broad peak around 10, K. These results suggest that one dimensional magnetic order along the c axis occurs in CePdSb at TC=17.5, K and three-dimensional order develops only below 10, K. It is found that ρ c increases below 8, K and 6, K for CePdSb and CePtSb, respectively, and RH(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.
