Polarized Neutron Diffraction: An Excellent Tool to Evidence the Magnetic Anisotropy—Structural Relationships in Molecules

Dominique Luneau,Béatrice Gillon

doi:10.3390/magnetochemistry7120158

Abstract

This publication reviews recent advances in polarized neutron diffraction (PND) studies of magnetic anisotropy in coordination compounds comprising d or f elements and having different nuclearities. All these studies illustrate the extent to which PND can provide precise and direct information on the relationship between molecular structure and the shape and axes of magnetic anisotropy of the individual metal sites. It makes this experimental technique (PND) an excellent tool to help in the design of molecular-based magnets and especially single-molecule magnets for which strong uniaxial magnetic anisotropy is required.

Highlights

With a magnetic moment and no charge, neutron provides several key scattering techniques dedicated to probing magnetic materials at the atomic level [1,2]
The strength of Polarized Neutron Diffraction (PND) is that mapping the spin density distribution from single crystal diffraction data provides direct information on the relationships between the crystal structure and the magnetic interactions pathways as well as the nature of intra- or inter-molecular magnetic couplings
We show that PND can help in such a knowledge as it knowledge as it allows a direct watching of the direction and strength of the principal allows a direct watching of the direction and strength of the principal magnetic anisotropy magnetic anisotropy axes magnetic of each individual magnetic metalto ions relative to the molaxes of each individual metal ions site relative thesite molecules orientation

Summary

Introduction

With a magnetic moment and no charge, neutron provides several key scattering techniques dedicated to probing magnetic materials at the atomic level [1,2]. The strength of PND is that mapping the spin density distribution from single crystal diffraction data provides direct information on the relationships between the crystal structure and the magnetic interactions pathways as well as the nature of intra- or inter-molecular magnetic couplings. The experimental flipping ratios contain all information on both the orientation and the magnitude of the atomic magnetic moments throughout the unit cell and can be expressed in terms of these susceptibility components through the magnetic structure factor FM by combining Equations (3) and (5). In the most general case (triclinic local symmetry), when the atom is located in general position, all six independent susceptibility components χij must be simultaneous refined This requires the measurement of at least three sets of flipping ratios collected for three orthogonal directions of the applied magnetic field.

PND Mapping of the Magnetic Anisotropy in Coordination Compounds

Transition Metal Compounds

Lanthanide Metal Compounds

Polynuclear Coordination Compounds

Conclusions