Related Experiment Video
Updated: May 31, 2026
Hyperspectral Imaging as a Tool to Study Optical Anisotropy in Lanthanide-Based Molecular Single Crystals
Published on: April 14, 2020
Crystal and magnetic structure of the R15Si9C compounds (R = Ho, Er, Tb)
Abstract:
The synthesis of the new compounds R(15)Si(9)C with R = Sm, Gd-Er, Y and R(15)Ge(9)C with R = Ce, Pr and Nd has been recently reported; these compounds crystallize in the hexagonal La(15)Ge(9)Fe structure type, hP50-P6(3)mc, Z = 2 (ordered superstructure of La(5)Ge(3) (Mn(5)Si(3)-type, hP 16-P6(3)/mcm, Z = 2)). Here we report the results of a neutron diffraction investigation that we have performed to study the crystal and magnetic structures of the R(15)Si(9)C compounds with R = Tb, Ho and Er. All three compounds see the establishment of commensurate magnetic order with a predominantly ferromagnetic interaction. Details of mixed antiferro-ferromagnetic spin arrangements (κ = [000]) (for Tb(15)Si(9)C and Ho(15)Si(9)C) or of purely ferromagnetic ordering (Er(15)Si(9)C), and of their temperature dependence, are given and linked to the different coordination of the four dissimilar rare earth sites. In the Tb and Ho compounds the thermal evolution of the magnetic moment values strongly differs between the different R sites. The position occupied by the principal carbon has been determined (Wyckoff site 2b) and the existence of a second position available for the interstitial carbon (Wyckoff site 2a) has been revealed for R = Ho, Tb. Moreover, in the Tb and Ho compounds the magnetic moment value of the rare earth site R4, surrounding the second interstitial carbon site, is strongly reduced if compared to the value on the other rare earth sites. The magnetic transition temperatures of all three compounds, i.e. T(C) = 130, 43 and 45 K for Tb(15)Si(9)C, Ho(15)Si(9)C and Er(15)Si(9)C, are remarkably high compared to those of the parent R(5)Si(3) compounds. The magnetic behaviour of the partly filled Tb(5)Si(3)C(0.25) is reported.
Related Concept Videos
02:58Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
02:42Ionic Crystal Structures
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
01:29Crystallographic Point Groups
02:42Valence Bond Theory
01:26Imperfections in Crystal Structure: Stoichiometric Point Defects