Molecular Magnetic Building Blocks

Published April 23, 2020

(top) Schematic of the new silicon-mediated replacement of fluorine atoms, resulting in the magnetic building block molecule shown at upper right. (bottom) Frequency vs magnetic field plot from which the much stronger magnetism along the z-axis (the steeper red line) can be deduced for the molecule with spin S = 3/2 and “M” representing a Rhenium atom.

This study reports the first transition metal compounds featuring mixed fluoride–cyanide ligands. A significant enhancement of the magnetic anisotropy, as compared to the pure fluoride ligated compounds, is demonstrated by combined analysis of high-field electron paramagnetic resonance (HF-EPR) spectroscopy and magnetization measurements.

What did scientists discover?

This study reports the first transition metal molecules featuring both fluorine and cyanide ligands (see "branches" attached to the metal atom (M) in the molecules at the top of the figure). A strong and significant enhancement of the non-uniformity of the magnetism, the "magnetic anisotropy" for the trans-[Re^IVF4(CN)₂]²- complex (shown in the upper right) was discovered by combined high-field magnetization and electron paramagnetic resonance (EPR) spectroscopy (see lower Figure).

Why is this important?

This research highlights an efficient new strategy for synthesizing molecular building blocks based on heavier transition metals that feature relatively large magnetic moments and very strong magnetic anisotropy. Such building blocks may form the basis for future high-performance magnetic materials used in high-density information storage applications.

Who did the research?

J.-L. Liu^1,2,3, K.S. Pedersen^1,4, S.M. Greer⁵, I. Oyarzabal^1,6, A. Mondal^1,7, S. Hill⁵, F. Wilhelm⁸, A. Rogalev⁸, A. Tressaud², E. Durand², J.R. Long⁹, R. Clérac^1,2

¹CRPP, Bordeaux; ²Univ. Bordeaux; ³Sun Yat-Sen Univ.; ⁴TU Denmark; ⁵FSU & National MagLab; ⁶Univ. Basque Country; ⁷IIS Bangalore; ⁸ESRF Grenoble; ⁹UC Berkeley & LBNL

Why did they need the MagLab?

EPR provides a direct measure of magnetic anisotropy, evidenced by the different steepness of the red, green, and blue lines in the lower figure. Magnetic anisotropy gives rise to broad EPR spectra that require very large magnetic fields in order to resolve all of the relevant details. For this reason, the measurements had to be performed at the MagLab’s Electron Magnetic Resonance facility.