Anisotropic magnetic properties of light rare-earth diantimonides

Results are presented of anisotropic temperature and field-dependent magnetization M(H,T) and resistivity ρ(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 CeSb2 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 M(H) and ρ(H) for H parallel(ab) in the magnetically ordered state. In addition, above 15 kG de Haas endash van Alphen oscillations are observed for SmSb2 and Shubnikov endash de Haas quantum oscillations are observed above ∼120kG for NdSb2 and SmSb2. The zero-field in-plane resistivity ρab of all of the compounds is metallic (dρ/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 SmSb2 has [ρ(55kG)-ρ(0)]/ρ(0)>50000% at T=2K and H parallel c. copyright 1998 The American Physical Society