Single-molecule magnets made easy

Using accessible techniques and a wealth of knowledge, researchers in Moscow have synthesised a new series of promising molecular magnets¹. The results, reported in the Russian Journal of Coordination Chemistry, advance the emerging technology of single-molecular magnets (SMMs).

Today’s memory chips are still based on the same fundamental fabrication technology as when they were first developed in the 1960s, involving etching a circuit pattern into a layered substrate. While the sophistication of the fabrication process and the resolution of the pattern have progressively improved, the minimum feature size, now measured in nanometres, is approaching the physical limits of the materials and fabrication methods. This means that further miniaturisation and performance advancements, such as memory capacity and speed, are becoming increasingly difficult to achieve.

Konstantin Babeshkin and colleagues from the Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences have been experimenting with an entirely different technology that could unlock a new era of memory chip development – molecular magnets.

“For several years now, we have been studying molecular magnets based on various elements, and most recently complex compounds of lanthanides, such as dysprosium and ytterbium,” says Babeshkin. “Each ‘bit’ created using molecular magnets is a thousand times smaller than the bits in current devices. The replacement of conventional storage devices with molecular magnets would therefore make it possible to achieve much higher storage capacities.”

Molecular magnets are analogous to the macro-scale magnets we’re familiar with, in that they retain their magnetism without an external magnetic field. The SMMs so far obtained can retain their magnetization for hundreds of seconds, which is sufficient for applications in volatile memory and low-power applications. However, the search is still on for compounds that are easier to prepare and with the best properties for use in memory devices.

“We prepared our complexes in alcohol at room temperature, and then dried the SMMs in air without high temperatures, aggressive media or inert atmosphere,” says Babeshkin.

The team confirmed the presence of molecular magnetism in all complexes containing the lanthanides dysprosium, erbium and ytterbium prepared with the ligand 2,2'-bipyridine. They also found that the ytterbium complex in particular displayed a strong resistance to magnetization reversal, attributed to the formation of a bicapped trigonal prism molecular structure at the complex’s core, which makes it potentially more stable in a memory application.

“This study helps improve our forecasting for obtaining subsequent SMMs with a similar nature,” Babeshkin says. “We are next planning to look for more effective SMMs containing other non-mainstream lanthanides such as erbium.”