Modulating magnetic anisotropy in Ln(iii) single-ion magnets using an external electric field

Single-molecule magnets have potential uses in several nanotechnology applications, including high-density information storage devices, the realisation of which lies in enhancing the barrier height for magnetisation reversal (U_eff). However, Ln(iii) single-ion magnets (SIMs) that have been reported recently reveal that the maximum value of U_eff values that can be obtained by modulating the ligand fields has already been achieved. Here, we have explored, using a combination of DFT and ab initio CASSCF calculations, a unique way to enhance the magnetisation reversal barrier using an oriented external electric field in three well-known Ln(iii) single-ion magnets: Dy(Py)₅(O^tBu)₂]⁺ (1), Er{N(SiMe₃)₂}₃Cl]⁻ (2) and Dy(Cp^Me3)Cl] (3). Our study reveals that, for apt molecules, if the appropriate direction and values of the electric fields are chosen, the barrier height can be enhanced by twice that of the limit set by the ligand field. The application of an electric field along the equatorial direction was found to be suitable for oblate shaped Dy(iii) complexes and an electric field along the axial direction was found to enhance the barrier height for a prolate Er(iii) complex. For complexes 2 and 3, the external electric field was able to magnify the barrier height to 2–3 times that of the original complexes. However, a moderate enhancement was noticed after application of the external electric field in the case of complex 1. This novel non-chemical fine-tuning approach to modulate magnetic anisotropy is expected to yield a new generation of SIMs.

Using a combination of theoretical tools, we show that the application of an external electric field in a certain direction can boost the axiality beyond that set by the ligands, opening up a new avenue for the generation of novel SIMs.