Anisotropic magnetic properties of light rare-earth diantimonides

Results are presented of anisotropic temperature and field-dependent magnetization M(H,T) and resistivity rho(H T) measurements on high quality single crystals of the light rare-earth diantimonides RSb2, R = La-Nd, Sm. All of these, excepting LaSb2, magnetically order at low temperatures, and for CeS2, and NdSb2 several magnetically ordered phases were observed in low-field magnetization and zero-field resistivity measurements. For R = Ce-Sm strong anisotropies, associated with crystalline electric field (CEF) splitting of the R3+ ion, were found in M(T) measurements both below and above magnetic ordering temperatures. Furthermore, for R = Ce-Nd metamagnetic transitions were observed in IM(H) and p(H) for H parallel to(ab) in the magnetically ordered state. In addition, above 15 kG de Haas-van Alphen oscillations are observed for SmSb2 and Shubnikov-de Haas quantum oscillations are observed above similar to 120 kG for NdSb2 and SmSb2. The zero-field in-plane resistivity rho(ab) of all of the compounds is metallic (d rho/dT>0), with residual resistance ratios ranging from 40 to 750. The c-axis resistivity is also metallic, but appears to be considerably larger than the in-plane value, consistent with the diantimonides being quasi-two-dimensional materials. The magnetoresistance of all members of the series is large, approximately Linear in H at moderate fields, and is also dependent on the relative orientation of the applied magnetic fields to the crystallographic axes. The extreme case of SmSb, has [rho(55 kG)-rho(0)]/rho(0)>50000% at T = 2 K and H parallel to c.