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∥(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 ~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 $H{∥}c.$