Spin Density Distribution and Interaction Mechanisms in Thiazyl-based Magnets

Spin Density Topology

“…Apart its function in SDFT, the spin density reflects the interactions that are taking place among the electron spins within a system and so also plays a fundamental role for understanding magnetic phenomena [ 2 , 3 , 4 , 5 , 6 ]. For example, the detailed knowledge of the spin density distribution in a molecule is essential for interpreting how spin polarization propagates in molecular complexes and crystals, allowing one to highlight and rationalize the various magnetic interactions as a function of molecular orientation and packing [ 4 , 7 , 8 ]. These interactions are comparable or even smaller in energy than the thermal energy, k B T , yet they can be exploited for designing magnetic materials with foreseeably important technological applications [ 3 ].…”

“…We are currently performing a few studies along these lines, using spin–polarized transition metal complexes as more difficult and, possibly, interesting cases. A next step will then involve the spin density topology of interacting complexes, like those studied in [ 4 , 5 , 6 , 7 , 8 ].…”

“…Both the mechanisms are always in operation and may either cooperate or oppose each other in determining the spin density magnitude and sign at any point in the real space. This description of the spin transmission mechanisms strictly applies to UHF (Unrestricted Hartree Fock) wavefunctions, while it is known that static and dynamic electron correlation effects, not considered in the Hartree–Fock formalism, also influence spin polarization [ 7 ].…”

“…These authors could derive both the electron position density ρ( r ) and its resolved α and β spin components using a spin–split version [ 24 ] of the original Hansen and Coppens multipolar model [ 25 ] able to refine the parameters of a multipolar model against both X–ray and polarized neutron diffraction (PND) data. Unlike nuclear and electron resonance techniques, such as NMR and EPR, the more demanding polarized neutron diffraction (PND) experiment has the key advantage to provide a direct mapping of the spin density in the periodic solid [ 6 , 7 , 23 ]. Deutsch et al [ 23 ] found that the (X–ray/PND)–refined ρ α and ρ β distributions were comparable to those determined through ab–initio methods.…”

Understanding magnetic interactions in the seriesA2FeX5⋅H2O(A=

“…This is particularly so in molecular magnetic systems where spin moments can be delocalized at the molecular level. [23][24][25] In particular, in the A 2 FeX 5 ·H 2 O series this knowledge would allow determination of whether the relatively high magnetic transition temperatures are due to an important spin delocalization from the iron ion toward the ligand atoms, as proposed in the previous paragraph. The existence of such a spin delocalization, which would strengthen the interaction between magnetic orbitals localized in different octahedra, is also supported by a reduced magnetic moment observed at the iron site in a powderneutron-diffraction experiment on K 2 FeCl 5 ·H 2 O.…”