# Crystal Structures, Optical Behavior, and Magnetic Properties in Hydrated Lanthanide Iron Sulfates

## TL;DR

This study explores the crystal structures, magnetic properties, and optical behavior of hydrated lanthanide iron sulfates, revealing differences between dihydrated and monohydrated compounds.

## Contribution

The paper reports new crystal structures and magnetic behaviors in a series of hydrated lanthanide iron sulfates.

## Key findings

- Dihydrated compounds form centrosymmetric structures with eight-coordinate lanthanide ions.
- Monohydrated compounds exhibit noncentrosymmetric structures with seven-coordinate lanthanide ions.
- Some compounds show antiferromagnetic ordering with distinct Néel temperatures.

## Abstract

Single crystals of
LnFe­(SO4)3(H2O)2 (Ln =
La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er,
Tm;
compounds 1–11) and LnFe­(SO4)3(H2O) (Ln = Tm, Yb, Lu; compounds 12–14) were synthesized under hydrothermal conditions. Single-crystal
X-ray diffraction (SCXRD) analysis revealed that the dihydrated compounds
(1–11) crystallize in centrosymmetric (CS) structures,
with the lanthanide ions adopting eight-coordinate geometries. In
contrast, the monohydrated compounds (12–14) exhibit
noncentrosymmetric (NCS) structures, where the lanthanide ions are
seven-coordinated. Vibrating sample magnetometry (VSM) confirmed that
compounds 2, 4, and 7–11 are paramagnetic below 400 K, with compound 8 displaying
the highest magnetic susceptibility. Compounds 1, 5, 6, 13, and 14 show
a sharp increase in magnetic susceptibility at Néel temperatures
(T
N) of approximately 72, 76, 70, 58,
and 56 K, respectively, indicating antiferromagnetic ordering. High-temperature
magnetic susceptibility measurements further support the presence
of antiferromagnetic transitions in these compounds. Second harmonic
generation (SHG) measurements showed that the noncentrosymmetric Yb
(compound 13) and Lu (compound 14) compounds
exhibit SHG intensities of 0.3× and 1.6× that of potassium
dihydrogen phosphate (KDP), respectively.