Orbital Magnetic
Moment and Single-Ion Magnetic Anisotropy
of the S = 1/2 K3[Fe(CN)6]
Compound: A Case Where the Orbital Magnetic Moment Dominates the Spin Magnetic Moment
posted on 2023-11-09, 11:08authored byMarius Retegan, Sadaf Fatima Jafri, Leonardo Curti, Laurent Lisnard, Edwige Otero, Eric Rivière, Maurits W. Haverkort, Anne Bleuzen, Philippe Sainctavit, Marie-Anne Arrio
The potassium hexacyanoferrate(III), K3[FeIII(CN)6], is known for its exceptional magnetic
anisotropy
among the 3d transition metal series. The Fe(III) ions are in the S = 1/2 low spin state imposed by the strong crystal field
of the cyanido ligands. A large orbital magnetic moment is expected
from previous publications. In the present work, X-ray magnetic circular
dichroism was recorded for a powder sample, allowing direct measurement
of the Fe(III) orbital magnetic moment. A combination of molecular
multiconfigurational ab initio and atomic ligand field multiplets
calculations provides the spin and orbital magnetic moments for the
[FeIII(CN)6]3− isolated cluster,
the crystallographic unit cell, and the powder sample. The calculations
of the angular dependencies of the spin and orbital magnetic moments
with the external magnetic induction direction reveal easy magnetization
axes for each S = 1/2 molecular entity and the crystal.
It also shows that the orbital magnetic moment dominates the spin
magnetic moment for all directions. Our measurements confirm that
the orbital magnetic moment contributes to 60% of the total magnetization
for the powder, which is in excellent agreement with our theoretical
predictions. An orbital magnetic moment greater than the spin magnetic
moment is exceptional for 3d transition metal ions. The impact of
crystal field strength and distortion, π back-bonding, spin–orbit
coupling, and external magnetic induction was analyzed, leading to
a deeper understanding of the spin and orbital magnetic anisotropies.