Magnetic properties and magnetic structures of the CeScSi-type RMgPb (R=Ce–Nd, Sm, Gd–Tm) compounds

Abstract

Investigations made by powder X-ray diffraction, magnetic measurements and neutron powder diffraction on the CeScSi-type ternary magnesium plumbides RMgPb (R=Ce–Nd, Sm, Gd–Tm) are reported. Macroscopic magnetic measurements performed in the 2–300K temperature range show that these compounds follow a Curie–Weiss law in the paramagnetic state (except SmMgPb) and behave antiferromagnetically at low temperature (TΝ≤61K). Field dependence of the magnetization performed at 5K evidence metamagnetic-like behaviors (Hcrit<7T). Neutron powder diffraction evidenced complex antiferromagnetic structures in fair agreement with the magnetic data. PrMgPb and NdMgPb compounds present a commensurate antiferromagnetic structure, while (Tb–Er)MgPb are characterized by incommensurate sine-wave modulated magnetic structure down to lower temperature or square-wave magnetic structure due to appearance of higher odd integer harmonics. CeMgPb and TmMgPb evidence more complex sine-wave modulated magnetic structures, never encountered with the CeScSi-type structure, characterized by two propagation vectors. These results are discussed and compared with those of the isotypic RMgSn compounds.