Electronic and magnetic materials are the central focus of the Leighton Group's research. We study a wide variety of materials, such as nanostructures, thin films, heterostructures, bulk polycrystals, and single crystals. We focus on topics with a strong fundamental science component that are in close proximity to applications in technology, including data storage and processing and electronic devices. Projects in our group feature fabrication of films and crystals, detailed structural and chemical characterization, and in-depth measurement by numerous techniques, including transport, neutron scattering, magnetometry, and heat capacity. Our work is highly collaborative, and we are involved in two UMN centers: the NSF Materials Research Science and Engineering Center and the DOE Center for Quantum Materials.
Current research projects include:
(i) Electrolyte gating of functional materials
As part of MRSEC IRG-1, the Leighton Group is applying electrolyte gating to a wide variety of materials systems, spanning oxides, sulfides, and organic semiconductors. Both electrostatic and electrochemical gating mechanisms are embraced. Current work focuses in particular on electrochemical control of the perovskite brownmillerite transformation in cobaltites, for control of electronic, magnetic, optical, thermal, and chemical properties.
(ii) Perovskite oxide films and heterostructures, particularly cobaltites
Perovskite oxide films and heterostructures have been a focus of our work for several years, particularly semiconducting and magnetic systems. As alluded to above, perovskite cobaltite films are of particular interest, for electrolyte gating and for fundamental studies of transport and magnetism.
(iii) Metallic delafossite materials, especially PdCoO2 and PdCrO2
We are actively working on bulk single crystals and thin films of metallic delafossites, which are the most conductive oxides known. Our recent work provided a comprehensive explanation for the origin of the ultrahigh residual conductivity of PdCoO2, while our current work focuses on PdCrO2, particularly the interplay between frustrated magnetism and other physical properties.
(iv) Metallic spin transport, particularly in non-local spin valves
For many years our group has maintained an effort in the area of metallic spin injection and relaxation, in lithographically patterned non-local spin valves. We perform fundamental studies understanding and quantifying Elliott-Yafet spin relaxation in light metals and alloys, as well as applied studies aimed at developing non-local spin valves for hard disk drive reader spin accumulation sensors.
(v) Transition metal sulfides, including the photovoltaic FeS2 and the Mott insulator NiS2
Our group has a long-standing effort aimed at developing pyrite FeS2 for low-cost, earth-abundant, non-toxic photovoltaics. Currently, much of this is based on single-crystal model systems, as well as the use of Minnesota natural resources for pyrite production. Expanding on this, we are also now working on the model antiferromagnetic Mott insulator NiS2, seeking to understand its surface conduction, and the delicate transition from Mott insulator to correlated metal.