Possible Long-periodic Magnetic Structure in SmPb3

Magnetic susceptibility and muon spin relaxation (µSR) measurements were performed on single-crystalline samples of SmPb 3 in order to investigate magnetic properties in an antiferromagnetic state below T N ∼5 K, where a simultaneous order of dipole and quadrupole moments had been proposed. A clear hysteretic behavior was observed in the temperature dependence of magnetic susceptibility, indicating the first-order nature of the phase transition. µSR data in a zero applied field indicate that an interstitial muon site splits into more than five magnetically inequivalent sites in the ordered state. In consideration of the most plausible muon site (3 d in Wycoff notation) in isomorphous compounds, this result suggests that a commensurate and possibly long-periodic magnetic structure is realized in SmPb 3 .