Event
Ph.D. Dissertation Defense - Jennifer Elizabeth DeMell
Friday, April 24, 2026
1:00 p.m.
AVW 1146
ANNOUNCEMENT: Ph.D. Dissertation Defense
Name: Jennifer Elizabeth DeMell
Committee:
Date/Time: Friday, April 24th, 2026, at 1 pm
Location: A.V. Williams Room 1146
Title: Novel Material Heterostructures for Spintronic Device Applications
Abstract:
The exponential growth of data generation globally is expected to exceed 200 zettabytes by the end of the year, largely driven by the increased usage of AI. The energy cost to move that data with conventional CMOS technology, compounded by the von Neumann bottleneck, is expected to double by the end of 2028. As the role of big data continues to grow, computing power and resources cannot keep up. Spintronic devices are an emerging pathway to solve the growing energy and scaling limitations of CMOS toward energy-efficient, higher-speed, non-volatile memory and logic. This dissertation focuses on investigating novel material low-dimensional spintronic devices through the scalable growth and integration of large-area magnetic thin films and heterostructures with an emphasis on improving operation temperature, spin transport, polarization efficiency, and spin diffusion length to inform on the functionality and versatility of these material systems and devices.
The first of these systems, a graphene/lead-tin-telluride heterostructure, is investigated, where a spin-split two-dimensional electron gas forms at the interface as a result of the polar catastrophe with strong spin–orbit coupling and proximity effects. A quantum phase transition observed at 40 K introduces a potential low-power switching mechanism, while room- and high-temperature measurements up to 500 K demonstrate a spin diffusion length of ~13 µm and spin polarization efficiencies of 10%. These results highlight the potential of this heterostructure for scalable, energy-efficient spintronic memory and logic applications.
The second system, manganese selenide (MnSe) is explored as an air-stable two-dimensional magnetic semiconductor grown via chemical vapor deposition with controllable α-, β-, and T-phase formation. Contrary to prior reports of ferromagnetism, β-phase MnSe exhibits antiferromagnetic ordering with a Néel temperature of 53 K, while T-phase MnSe demonstrates strong interlayer antiferromagnetic coupling and an exchange bias of 22 Oe persisting up to 300 K. Weak antilocalization observed in magnetotransport measurements further indicates strong spin–orbit interactions and magnetic character. Together, these findings identify T-phase MnSe as a promising, scalable material for incorporation into low-dimensional spintronic devices.
The work in this dissertation demonstrates a viable pathway toward energy efficient, scalable spintronic technologies based on low-dimensional magnetic materials and heterostructures.
