After receiving his doctoral degree in physics from Rutgers-The State University of New Jersey in 2006, Fennie spent two years at The Center for Nanoscale Materials at Argonne National Laboratory as the Nicholas Metropolis Fellow. He joined the Cornell faculty in July of 2008 and works in the broad area of computational/theoretical materials physics including Materials-by-Design. 

Research Interest

Our interests lie at the intersection of materials science and condensed matter physics and can be broadly characterized as centered on the use of theory to discover and elucidate new structurally and chemically complex bulk solids and nanostructures, with a particular interest in dielectric, magnetic, and optical properties and in structural phase transitions.

Materials displaying complex crystalline motifs, e.g., perovskites, spinels, and pyrochlores, are strikingly rich systems to study such emergent phenomena. The main thrust of our research is to establish an understanding of how to control the interplay between the diverse microscopic degrees of freedom prevalent in these systems in order to create new and targeted macroscopic properties, and to design the never-before-seen material realizations.

In order to accomplish these goals we use a combination of microscopic models, symmetry principles, and crystal chemistry to develop a general set of chemically and physically intuitive mechanisms and design rules. We then use first-principles computational techniques such as density-functional theory to screen potential realizations of these rationalized design criteria; first-principles density-functional methods recently have proved a powerful tool for studying the properties of complex materials at the level of atoms and electrons, without the need for empirical input.

Why Materials-by-Design

The design and discovery of new materials with interesting properties is crucial for future scientific progress across many disciplines. The traditional exploratory route is quite demanding, as there are an enormous number of possible tertiary and quaternary bulk compounds that have yet to be unearthed, much less characterized. Additionally, recent advances in synthesis techniques facilitate tailoring and enhancing the properties of complex materials at the nanoscale, greatly extending the design variables. A theoretical, rational approach can accelerate scientific innovation by providing efficient strategies to survey this vast space of possible materials to target for synthesis.

Current Research

• Multifunctional materials: For example, of great interest to me is a class of multifunctional materials that are rarely found in nature, multiferroics for which a spontaneous magnetism not only coexists with but also is strongly coupled to a spontaneous electrical polarization.
• Nanoscale piezoelectricity and ferroelectricity  
• The epitaxial stabilization of novel phases at the nanoscale  
• The question of “how do we start with a model and end with a real material”  
• Mechanisms of structural and magnetic phase transitions including spin-lattice coupling and frustration  
• Optical properties of structurally and chemically complex materials  
  

• Claude Ederer and Craig J. Fennie, “Electric-field switchable magnetization via the Dzyaloshinskii -Moriya interaction: FeTiO₃ versus BiFeO₃,” invited paper, Special Issue on Multiferroics,  J. Physics: Condensed Matter, in press.  
• Craig J. Fennie, “Ferroelectrically induced weak-ferromagnetism by design,” Physical Review Letters 100, 167203 (2008).
• Craig J. Fennieand Karin M. Rabe, “Magnetic and electric phase control in epitaxial EuTiO₃ from first principles,” Physical Review Letters 97, 267602 (2006).
• Craig J. Fennieand Karin M. Rabe, “Magnetically-induced phonon anisotropy in ZnCr₂O₄ from first principles,” Physical Review Letters 96, 205505 (2006).
• Craig J. Fennieand Karin M. Rabe, “The ferroelectric transition in YMnO₃ from first principles,” Physical Review B 72,100103 R (2005).