CAREER: Frustration on Nanomagnetic Lattices

University Of Maryland, College Park, College Park MD

Investigators

Abstract

*** Non-Technical *** When substances freeze from the liquid state, such as water forming ice, their atoms usually lock into a perfect repeating pattern, known as a crystal. This is because the perfect pattern usually has a much lower energy. However, some materials have many possible patterns at the same or very similar energies, and as a result these substances form imperfect solids, with disordered arrangements of the different patterns. Substances with these peculiar properties are said to be frustrated. This project will study the concept of frustration and how it can arise as a consequence of certain crystal structures. Two early-career scientists, a postdoctoral researcher and a graduate student, will be guided by their advisor to conduct experiments with very small nano-scale magnets arranged through semiconductor processing techniques to form crystal structures that are known to show the effects of frustration. These scientists will conduct experiments attempting to discover whether the magnets can be encouraged to align themselves into a repeating pattern, overcoming the effects of frustration. Through collaboration with an area high school that serves predominantly African-American students, the project will additionally include the assistance of a high school student, who will learn the techniques of science and technology research and bring the excitement of science and engineering back to their classroom with an assigned presentation. Together these activities will help to broaden and enliven participation in science and engineering, training the next generation of scientists and increasing American competitiveness in key technology areas. *** Technical *** This proposal describes a research and education plan that will expand the physical underpinnings of frustrated magnetism. This will be achieved through studies of magnetic structure and dynamics of artificial spin ice materials. Students will fabricate frustrated nanomagnetic structures using electron beam lithography, and study their magnetic order with real-time Lorentz-mode transmission electron microscopy (LTEM). The project will have four primary research thrusts, as follows: I. to understand the dynamics of these artificial materials, including the relevance and properties of magnetic monopoles, emergent excitations which facilitate the internal magnetic switching of these materials, II. to explore the role that disorder plays in the frustration of these systems, which are otherwise geometrically frustrated (i.e. does disorder remove or exacerbate the frustration?), III. to discover routes by which these materials can reach their ground states, or to gain a better understanding of the kinetic roadblocks preventing this, and IV. to use this new research tool to create new spin ice materials that would otherwise be difficult to synthesize as natural materials and to explore the unique properties of these new synthetic artificial spin ices. Additionally, a student from a minority-serving area high school will participate in the research through a research practicum as part of their regular curriculum on an annual basis.