Dr. Randall McClain and Dr. Ben Harvey, research chemists working for Naval Air Warfare Center Weapons Division, published groundbreaking research in the field of single molecule magnets in the Jan. 14 edition of Science magazine, the flagship journal of the American Association for the Advancement of Science.
“Science is one of the most prestigious U.S.-based scientific journals,” Harvey said. “The articles need to describe ground-breaking work that is of interest to all scientists, and most scientists never get this opportunity.”
NAWCWD researchers began studying single molecule magnets (SMMs) in late 2017. McClain, at the time National Research Council Postdoctoral Fellow who has since transitioned to a full-time NAWCWD employee, synthesized and characterized the SMMs while Harvey served as the principal investigator, directing the research and mentoring McClain during his fellowship and subsequent transition to full time federal service. He also directed the research program and helped establish collaboration partnerships with academic organizations.
Conventional magnets, like those on your refrigerator or the powerful rare earth-based magnets used in computer hard drives, are composed of a network of inorganic structures with aligned electron spins. In contrast, SMMs are magnetic molecules that possess an energy barrier to re-orientation of their molecular spin. These molecules produce localized magnetic fields and are essentially the smallest possible magnets. These materials have the potential to greatly increase the magnetic storage density of hard drives or to induce magnetic fields with incredible precision, potentially enabling the development of novel components useful for quantum computers.
However, despite the promise of SMMs, these exotic materials can be easily disrupted by their environment, which eliminates their magnetic behavior, McClain explained. In fact, most SMMs only exhibit their magnetic properties at temperatures near absolute zero. McClain’s work has shown that by controlling the SMM environment through molecular design, operating temperatures up to 80 K can be realized. This advance makes the use of SMMs feasible in practical devices.
McClain and Harvey synthesized a series of novel lanthanide dimers that exhibit lanthanide-lanthanide bonds, a bonding interaction not previously described in the literature. This interaction aligns the magnetic moments of the metal centers.
“Using dysprosium as the lanthanide resulted in the best SMM ever created by any comparative metric,” Harvey said. “This new material exhibits slow magnetic relaxation at high temperatures and has an extremely high barrier to magnetic reversal. This type of hard magnetism at elevated temperature is unprecedented for SMMs and represents a major breakthrough.”
“Leveraging collaborations with academic institutions can deliver next-generation materials and devices for use in both commercial and DoD applications,” he added.
The NAWCWD team collaborated with academic partners, with researchers at the University of California, Berkeley conducting the magnetic characterization of the molecules and researchers at the University of Manchester conducting calculations to support and explain the team’s experimental results.
“This disruptive technology showcases the diverse talent of the Research Department at NAWCWD and is just one more example of the continued outcome based focus our researchers have for the safety of the United States,” said Harlan Kooima, NAWCWD’s Research and Development Group director.
“High performance SMMs and related molecules offer the promise of transformational advances in data storage, high performance computing and quantum information science, all areas of crucial strategic importance,” Harvey said, noting that researchers at NAWCWD are continuing this line of research with the hope of transitioning to the fabrication and testing of devices based on the new SMMs.