- Postdoctoral Appointee, Argonne National Laboratory, 2012-2015
- PhD, Princeton University, 2012
- BS, Case Western Reserve University, 2007
The Allred group specializes in the discovery and characterization of new inorganic materials with functional properties. Solid state devices are ubiquitous in energy and information technologies, but we often lack the chemical tools to control and manipulate the underlying charge and/or spin dynamics. This requires a fundamental understanding of how these emergent properties can be tied back to the local bonding environment.
We emphasize using state-of–the-art x-ray and neutron diffraction techniques to investigate the atomic positions both on the long-range averaged limit and the microscopic local scale in bulk solid state compounds. We leverage what we learn to guide our synthesis efforts of future materials with desired properties. For example:
The long-range ordering of magnetic moments depends on the combination of competing interactions. Many facets of how this works are still not understood, due to the difficulty in dealing with correlated electrons in electronic structure models. What is known is that this complex interplay gives rise to the many different types of ordering that span various regimes of bonding—from localized to delocalized, ionic to covalent. One way to improve our understanding of these interactions is to tune material properties in order to stabilize unusual ground states. For example, one strategy is to tune across the boundary between localized and delocalized electronic states.
Sometimes magnetism is only one part of a rich tapestry of interconnected properties. Multiferroics are materials that exhibit multiple primary types of ferroic ordering, such as ferromagnetism or ferroelectricity. In many cases the way these effects interact is obscured by details of the electronic or atomic structure. Emerging diffraction technologies provide new avenues for teasing out the important bonding interactions from the collective ones throughout a crystal. These materials can be used in the next generation of sensor technologies, which depend on a combination of multiple order parameters—e.g. orbitals, spins, charge—that couple in a controllable manner.
Double-Q spin density wave in iron arsenide superconductors, J. M. Allred, K. M. Taddei, D. E. Bugaris, M. J. Krogstad, S. H. Lapidus, D. Y. Chung, H. Claus, M. G. Kanatzidis, D. E. Brown, J. Kang, R. M. Fernandes, I. Eremin, S. Rosenkranz, O. Chmaissem, and R. Osborn Nature Physics, (2016), DOI: 10.1038/NPHYS3629
Tuning the Magnetic Properties of New Layered Iron Chalcogenides (BaF)2Fe2-xQ3 (Q=S, Se) by Changing the Defect Concentration on the Iron Sublattice M. Sturza, J. M. Allred, C. D. Malliakas, D. E. Bugaris, F. Han, D. Y. Chung and M. G. Kanatzidis, Chem. Mater.(2015), 27 (9), pp 3280-3290
Brownmillerite Ca2Co2O5: Synthesis, Stability, and Re-entrant Single Crystal Structural Transitions, J. Zhang, H. Zheng, C. D. Malliakas, J. M. Allred, Y. Ren, Q. Li, T.-H. Han, and J. F. Mitchell, Chem. Mater., (2014) 26 (24) pp 7172-7182
First order, coincident structural and magnetic phase transitions in BaFe2(As1-xPx)2revealed by high-resolution neutron diffraction, J. M. Allred, K. M. Taddei, D. E. Bugaris, S. Avci, O. Chmaissem, D. Brown, D.Y. Chung, H. Klaus, A. Huq, M. G. Kanatzidis, O. Chmaissem, S. Rosenkranz, R. Osborn, Phys. Rev. B 90, (2014) 104513
Magnetically driven suppression of nematic order in an iron based superconductor. S. Avci, O. Chmaissem, J.M. Allred, S. Rosenkranz, I. Eremin, A. V. Chubukov, D. E. Bugaris, D.Y. Chung, M.G. Kanatzidis, J.-P. Castellan, J.A. Schlueter, H. Claus, D.D. Khalyavin, P. Manuel, A. Daoud-Aladine, R. Osborn Nat. Commun., 5:3845 (2014) doi: 10.1038/ncomms4845
Structural, magnetic, and superconducting properties of Ba1-xNaxFe2As2, S. Avci, J.M. Allred, O. Chmaissem, D.Y. Chung, S. Rosenkranz, J.A. Schlueter, H. Claus, A. Daoud-Aladine, D.D. Khalyavin, P. Manuel, A. Llobet, M.R. Suchomel, M.G. Kanatzidis, R. Osborn, Phys. Rev. B, 88 (2013) 094510
Spontaneous Formation of Zigzag Chains at the Metal-Insulator Transition in the beta-Pyrochlore CsW2O6, D. Hirai, M. Bremholm, J.M. Allred, J. Krizan, L.M. Schoop, Q. Huang, J. Tao, R.J. Cava, Phys. Rev. Lett., 110 (2013) 166402
Crystal Structures of the high temperature forms of V8O15 and V9O17 and Structural Trends in the VnO2n-1 Magnéli Series, J.M. Allred and R.J. Cava, J. Sol. St. Chem, 198 (2013) 10-17
Ordered CoSn-type ternary phases in Co3Sn3-xGex, J.M. Allred, Shuang Jia, M. Bremholm, B.C. Chan, and R.J. Cava, J. Alloys Comp., 539 (2012) 137-143
High Tc Electron Doped Ca10(Pt3As8)(Fe2As2)5 and Ca10(Pt4As8)(Fe2As2)5Superconductors with Skutterudite Intermediary Layers, N. Ni, J. M. Allred, B. C. Chan, and R. J. Cava ,Proc. Natl. Acad. Sci., 108 (2011) E1021
Na27Ru14O48: A new mixed-valence sodium ruthenate with heptameric plaquettes, J.M. Allred, L.M. Wang, P. Khalifah, and R.J. Cava , J. Sol. St. Chem., 184 (2011) 44-51