Ligand Effects toward the Modulation of Magnetic Anisotropy and Design of Magnetic Systems with Desired Anisotropy Characteristics

Abstract

Magnetic anisotropy of a set of octahedral Cr(III) complexes is studied theoretically. The magnetic anisotropy is quantified in terms of zero-field splitting (ZFS) parameter D, which appeared sensitive toward ligand substitution. The increased π-donation capacity of the ligand enhances the magnetic anisotropy of the complexes. The axial π-donor ligand of a complex is found to produce an easy-plane type (D > 0) magnetic anisotropy, while the replacement of the axial ligands with π-acceptors entails the inversion of magnetic anisotropy into the easy-axis type (D < 0). This observation enables one to fabricate a single molecule magnet for which easy-axis type magnetic anisotropy is an indispensable criterion. The equatorial ligands are also found to play a role in tuning the magnetic anisotropy. The magnetic anisotropy property is also correlated with the nonlinear optical (NLO) response. The value of the first hyperpolarizability varies proportionately with the magnitude of the ZFS parameter. Finally, it has also been shown that a rational design of simple octahedral complexes with desired anisotropy characteristics is possible through the proper ligand selection.

Reversible solvatomagnetic switching in a single-ion magnet from an entatic state

“…32,33 Being a non-cooperative property of an isolated molecule, the SIM behaviour depends on subtle and small structural variations in the metal coordination environment that directly determine the nature and magnitude of the local single-ion magnetic anisotropy, e.g. peripheral ligand modifications.…”

Elucidating the 3d Electronic Configuration in Manganese Phthalocyanine

“…In fact, it has been recently proven that the addition or removal of ligands could be used to modulate the direction of the spontaneous magnetization. 13 Because the highest occupied 3d orbital and, respectively, the lowest unoccupied bring, in general, the largest contribution to the anisotropy, understanding the manner in which the metal states are populated may prove to be essential in both clarifying the origins of the molecular magnetic anisotropy as well as in reversibly controlling its orientation (from uniaxial to in plane and vice versa).…”

On the Control of Magnetic Anisotropy through an External Electric Field

“…Hence, from the above discussion, it is evident that the natural tendency of the electrons to flow towards the π‐acceptor NCS ligands is developed at a field strength higher than that of the critical field. It follows from our previous work that the π‐accepting tendency of the ligands exerts easy‐axis‐type magnetic anisotropy ( D <0) in a molecule 14. Thus, it can be concluded that the switch in the D value arises from metal‐to‐ligand back charge transfer in the molecule facilitated by exposure to the external electric field.…”

“…It follows from our previous work that the p-accepting tendency of the ligands exerts easyaxis-type magnetic anisotropy (D < 0) in a molecule. [14] Thus, it can be concluded that the switch in the D value arises from metal-to-ligand back charge transfer in the molecule facilitated by exposure to the external electric field. A similar and more interesting portrayal of the phenomenon is found in the spin density plots depicted in Figure 4.…”

“…The modulation of the ZFS parameter by ligand substitution has recently been studied in the framework of DFT. [14] Structural modification in an octahedral Cr III system can switch the magnetization behavior of a molecule from easy-plane to easyaxis type. Herein, we investigate the effect of an external electric field on the ZFS parameter of a pseudo-octahedral [Co II -(dmphen) 2 (NCS) 2 ] complex (dmphen = 2,9-dimethyl-1,10-phenanthroline; Figure 1) to control magnetization through external stimuli.…”