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Xue Group Published in Chem. Eur. J.

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The Xue Group published their research “Applying Unconventional Spectroscopies to the Single-Molecule Magnets, Co(PPh3)2X2 (X=Cl, Br, I): Unveiling Magnetic Transitions and Spin-Phonon Coupling” in Chemistry—A European Journal. Alex Bone is a graduate student in the Xue and first author of this paper. 

Large separation of magnetic levels and slow relaxation in metal complexes are desirable properties of single-molecule magnets (SMMs). Spin-phonon coupling (interactions of magnetic levels with phonons) is ubiquitous, leading to magnetic relaxation and loss of memory in SMMs and quantum coherence in qubits.

“Direct observation of magnetic transitions and spin-phonon coupling in molecules is challenging,” Bone said. “We have found that far-IR magnetic spectra (FIRMS) of Co(PPh3)2X2 (Co-X; X=Cl, Br, I) reveal rarely observed spin-phonon coupling as avoided crossings between magnetic and u-symmetry phonon transitions.”

Inelastic neutron scattering (INS) gives phonon spectra. Calculations using VASP and phonopy programs gave phonon symmetries and movies. Magnetic transitions among zero-field split (ZFS) levels of the S=3/2 electronic ground state were probed by INS, high-frequency and -field EPR (HFEPR), FIRMS, and frequency-domain FT terahertz EPR (FD-FT THz-EPR), giving magnetic excitation spectra and determining ZFS parameters (D, E) and g values. Ligand-field theory (LFT) was used to analyze earlier electronic absorption spectra and give calculated ZFS parameters matching those from the experiments. DFT calculations also gave spin densities in Co-X, showing that the larger Co(II) spin density in a molecule, the larger its ZFS magnitude.

The current work reveals dynamics of magnetic and phonon excitations in SMMs. Studies of such couplings in the future would help to understand how spin-phonon coupling may lead to magnetic relaxation and develop guidance to control such coupling.

Bone Selected to Attend NX School

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Alex Bone, graduate student in the Xue Group, has been selected to attend the Twenty-Third National School on Neutron and X-ray Scattering to be held virtually from Oak Ridge National Laboratory and Argonne National Laboratory.

Due to the COVID-19 pandemic, the National School on Neutron and X-ray Scattering (NX School) will be held virtually from July 12-30, 2021. The first week of the program will consist of half day lecture sessions, the second and third week will be lectures, remote experiments and data analysis tutorials.

The main purpose of the National School on Neutron and X-ray Scattering is to educate graduate students in the use of major neutron and x-ray facilities. Lectures, presented by researchers from academia, industry, and national laboratories, include basic tutorials on the principles of scattering theory and the characteristics of the sources, as well as seminars on the application of scattering methods to a variety of scientific subjects. Students will conduct short remote experiments at Argonne’s Advanced Photon Source and at Oak Ridge National Laboratory’s Spallation Neutron Source and High Flux Isotope Reactor, which provides hands-on experience using neutron and synchrotron sources.

This year’s NX School will be three weeks in length. The first week will consist of half day lecture sessions. The second two weeks will be full-time consisting of lectures and remote experiments.

Jointly Conducted by: Argonne National Laboratory’s, Advanced Photon Source and Materials Science Division, and Oak Ridge National Laboratory’s Neutron Sciences Directorate and Materials Science and Technology Division.

The School is supported by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, and Materials Sciences and Engineering Division.

Tin Awarded Shull Wollan Center Graduate Research Fellowship

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Pagnareach (Reach) Tin, graduate student in the Xue Group, has been awarded the Shull Wollan Center Graduate Research Fellowship for Spring 2021.

The Shull Wollan Center Graduate Research Fellowship Program has been designed to recognize and support outstanding graduate students in neutron science disciplines who are pursuing research-based doctoral degrees at the University of Tennessee, Knoxville. 

The Shull Wollan Center Graduate Research Fellowship will be awarded to two UTK doctoral students with majors in physics, chemistry, materials science and engineering, biology, or a related area who are engaged in active research as part of their PhD thesis.  Successful applicants will be awarded a monthly stipend for January through June 2021.