Strong magnetic coupling in the hexagonal R5Pb3 compounds (R = Gd-Tm)

TL;DR

This study synthesizes and analyzes R5Pb3 compounds (R = Gd-Tm), revealing high magnetic ordering temperatures, complex magnetic phases, and incommensurate magnetic structures influenced by crystal electric field effects.

Contribution

It provides the first comprehensive structural and magnetic characterization of R5Pb3 compounds across R = Gd to Tm, highlighting their high ordering temperatures and complex magnetic behaviors.

Findings

High magnetic ordering temperatures up to 275 K for R=Gd.

Presence of multiple magnetic phase transitions.

Incommensurate magnetic structures with spin modulation.

Abstract

We have synthesized R5Pb3 (R = Gd-Tm) compounds in polycrystalline form and performed structural analysis, magnetization, and neutron scattering measurements. For all R5Pb3 reported here the Weiss temperatures {\theta}W are several times smaller than the ordering temperatures TORD, while the latter are remarkably high (TORD up to 275 K for R = Gd) compared to other known R-M binaries (M = Si, Ge, Sn and Sb). The magnetic order changes from ferromagnetic in R = Gd, Tb to antiferromagnetic in R = Dy-Tm. Below TORD, the magnetization measurements together with neutron powder diffraction show complex magnetic behavior and reveal the existence of up to three additional phase transitions. We believe this to be a result of crystal electric field effects responsible for high magnetocrystalline anisotropy. The R5Pb3 magnetic unit cells for R = Tb-Tm can be described with incommensurate magnetic wave vectors with spin modulation either along the c axis in R = Tb, Er and Tm or within the ab-plane in R = Dy and Ho.