Magnetism in vanadium-based intercalation compounds of transition metal dichalcogenides

Non-technical description:

Exotic magnetic materials hold great promise for next-generation devices that leverage the spin of the electron to store information (so-called spintronic devices). Such devices hold the promise to possess higher storage densities, greater security to external probes, lower power consumption, and faster switching dynamics. Altermagnets are a recently identified class of magnetic material that display highly attractive functional properties that are more traditionally associated with ferromagnets such as iron.

These novel materials offer advantages for electrical control and read-out compared to traditional antiferromagnets but still possess the properties that are desirable for ultra-compact, miniaturized devices. With this project, supported by the Solid State and Materials Chemistry Program in NSF’s Division of Materials Research, researchers at the University of California Berkeley synthesize materials that have been proposed as potential altermagnets but not have not yet been realized.

Prof. Bediako and his research group investigate these materials to understand how their solid-state structure and compositional variations dictate their magnetic and electronic properties. These research efforts are integrated with education and outreach initiatives that seek to broaden participation in STEM education and scientific research, in particular through the tutoring of incarcerated students at Mount Tamalpais College at San Quentin State Rehabilitation Center in mathematics, science, and computer science.

Technical description:

Intercalation compounds of transition metal dichalcogenides (TMDs) are a highly tunable platform for designing the magnetic properties of materials for next-generation spintronics. In this class of solids, changing the transition metal dichalcogenide host lattice, the intercalant identity, and intercalation stoichiometry modulates emergent magnetic behavior.

The magnetic properties of these intercalation compounds are also highly sensitive to the nature of defects/disorder within the intercalant lattice. Compared to studies of Cr, Mn, Fe, and Co intercalation in TMDs, there are very limited experimental data in the literature on TMD intercalation compounds of vanadium, despite a few recently having been theoretically proposed as a candidate altermagnetic material - a recently proposed magnetic phase classification that has distinctive electronic and spintronic properties that set it apart from conventional antiferromagnets.

More broadly, for the family of V-intercalated TMDs, an understanding of how intercalant stoichiometry alters magnetic properties is completely lacking. This knowledge gap presents critical impediments for an intuitive, chemical understanding of how d-electron count, intercalant structure, and magnetic exchange dictate the varied magnetic properties in intercalated TMDs.

In turn, this knowledge gap impedes the rational design of magnetic materials with desirable properties (higher operating temperatures, more efficient spin–charge conversion for spintronics, etc.). To address this challenge, researchers at the University of California Berkeley focus on the synthesis, structural characterization of V-intercalated TMDs and elucidation of connections between synthetic conditions, structure, and physical properties.

They use a combination of solid-state synthesis, crystal growth, x-ray and electron diffraction, neutron scattering, magnetometry, and electronic transport measurements to unveil the fundamental knowledge needed to synthesize high purity materials and control exotic magnetic behavior. This work deepens the understanding of fundamental structure-property relationships in intercalation compounds and builds a framework for understanding how to manipulate magnetic and electronic phenomena through solid-state synthesis and materials chemistry principles.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.