The crystallographic, magnetic and electronic properties of RM 2X 2 (R  La, Ce, Pr; M  Cu, Ni; X  Sn, Sb)

Abstract

The crystallographic structure, magnetic properties and X-ray photoemission spectra of PrNi 2Sn 2PrCu 2Sn 2, PrNi 2Sb 2 and PrCu 2Sb 2 are investigated. Two phases occur for PrNi 2Sn 2 and PrNi 2Sb 2 depending on preparation, the first being tetragonal, the other monoclinic. The compounds are antiferromagnets below T ⋍ 5 K , in the magnetic field a phase transition of the spin-flip type is observed. The critical magnetic fields are small. The magnetic susceptibility suggests that Pr is nearly trivalent and the crystal field splittings are weak. We also report valence band and 3d core-level X-ray photoemission spectroscopy (XPS) data of LaM 2X 2, CeM 2X 2 and PrM 2X 2, where M  Ni, Cu and X  Sn, Sb. The light rare-earth 3d spectra show in these compounds a satellite structure, which we discuss. We attempt an analysis of these core-level spectra using the Gunnarsson-Schönhammer model. A large hybridization of the f orbitals with a conduction band is characteristic for all the investigated compounds. The XPS valence bands are compared with self-consistent band structure calculations of the LMTO type, and are discussed.