Light-Induced Magnetic Switching as a Trigger for Phase Transitions in Molecular Materials

Florida State University, Tallahassee FL

Investigators

Abstract

With this award, the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division is funding a collaborative research team led by Professors Mykhailo Shatruk and Nar S. Dalal of the Department of Chemistry and Biochemistry at Florida State University to investigate photoresponsive molecules that can translate the action of heat, pressure, or light irradiation into substantial changes into changes in the magnetic and structural properties of materials. The successful implementation of this design principle could potentially lead to new ferroelectrics and conductors that could be actuated by the action of light. Leveraging the expertise of the Shatruk and Dalal groups in the synthesis and characterization of magnetic and photomagnetic materials, ferroelectric materials, and organic conductors, the team aims to create novel multifunctional materials that can be employed in electronic devices or light-activated switches. The project will actively involve graduate and undergraduate students in laboratory research, including students from groups underrepresented in physical sciences. The research team plans to continue their Undergraduate Summer Schools on Magnetism, first organized in Summers of 2012 and 2014, with the next school scheduled for Summer 2016. This project targets the synthesis and characterization of photoresponsive molecules capable of translating temperature-, pressure-, or light-induced changes in the magnetic state of the system into substantial structural changes, which consequently would trigger another type of phase transition in the material. The Shatruk/Dalal team will explore approaches to couple the photoinduced magnetic bistability at the molecular level to long-range metal-insulator transitions and ferroic orderings (magnetic or electric) in molecule-based materials. In particular, the team will study Fe(II) complexes with spin crossover (SCO) behavior, which stems from the temperature or light-induced transition between diamagnetic low-spin (LS) and paramagnetic high-spin (HS) states of the Fe(II) ion. The photoinduced LS to HS transitions will be invoked in order to achieve properties such as ferroelectricity and conductivity via photoexcitation. Materials in which SCO coexists with conductivity will provide a platform to test the effects of concerted atomic displacements associated with SCO on the conductivity of the organic substructure, with the potential to achieve photoinduced superconductivity via chemical compression. Another thrust aims to explore photoinduced magnetic switching, akin to SCO, in metal-free organic systems, where the change in the magnetic state is due to interconversions between paramagnetic radicals and diamagnetic dimers of radicals. The study of such metal-free systems could open up a new area in the molecular magnetism field that would parallel the studies currently performed on transition metal complexes.