We synthesized the R5Pb3 (R = Gd-Tm) compounds in polycrystalline form and performed neutron scattering and magnetization measurements. For most magnetic compounds, the Weiss temperature θW (a measure of the magnetic interaction strength) is comparable or larger then the magnetic ordering temperature Tord. But in the R5Pb3 (R = Gd - Tm) θW values 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 rare earth compounds. The magnetic order changes from ferromagnetic (FM) in R = Gd, Tb to antiferromagnetic (AFM) in R = Dy-Tm, and multiple magnetic phase transitions are observed in most these systems, a likely result of large anisotropic exchange or high magnetocrystalline anisotropy.
Remarkably high ordering temperatures in the R5Pb3 systems
Yufei Hu, Chih-Wei Chen, Huibo Cao, F. Makhmudov, Jason H. Grebenkemper, M. N. Abdusalyamova, Emilia Morosan, and Susan M. Kauzlarich, "Tuning Magnetism of [MnSb4]9– Cluster in Yb14MnSb11 through Chemical Substitutions on Yb Sites: Appearance and Disappearance of Spin Reorientation". J. Am. Chem. Soc. 138, (2016)
A. Marcinkova, C. Cruz, J. Yip, L. L. Zhao, J. K. Wang, E. Svanidze, E. Morosan, "Strong magnetic coupling in the hexagonal R5Pb3 compounds (R= Gd-Tm)" J. Magn. Magn. Mater. 384, 192 (2015)
Tuning magnetism in Yb14MnSb11 through chemical substitution
We synthesized Yb14-xRExMnSb11 single crystals (RE = Pr, Nd, Sm, Gd) and performed MPMS measurements, powder X-ray diffraction, neutron diffraction, and electron microprobe analysis. As RE is trivalent one additional electron is added to the system. All compounds show ferromagnetic order between 39 K and 52 K attributed to [MnSb4]9- clusters. For RE = Nd, Pr temperature dependent DC magnetization measurements show a sharp downturn right below the ferromagnetic transition temperature. Neutron diffraction shows this is because of a spin reorganization from the ab-plane to c-plane. The variation of magnetic behavior is caused by various RE substitution which leads to different interactions of 4f- and 3d-orbitals.