Author: hillepr

Dr. Kavipriya Thangavel, our new postdoctoral associate in the Hill Group, holds Bachelor’s and Master’s degrees in Physics from Bharathiar University, India. She began her research journey as a Junior Research Fellow at the Department of Physics, Indian Institute of Technology Madras (IITM, India), investigating the structural and magnetic transitions in electron-doped Manganite Oxide and exploring its magnetocaloric Properties. Kavi furthered her academic pursuits through a joint doctoral program facilitated by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Actions Fellowship – PARACAT (https://paracat.eu/wp/). This endeavor led her to obtain double doctoral degrees from Leipzig University (Physics) and Cardiff University (Chemistry). In this PhD program, her work focus on the ‘Elucidation of the Role of Paramagnetic Valence States of High Spin Transition Metal Ions in Metal-Organic Frameworks by EPR Spectroscopy’.

She is now part of the Hill Group at the National High Magnetic Field Laboratory, set to delve into research using the W-band HiPER spectrometer. Welcome aboard!

Creating the next generation of quantum systems requires control and tunability, which are key features of molecules. To design these systems, one must consider the ground-state and excited-state manifolds. One class of systems with promise for quantum sensing applications, which require water solubility, are d⁸ Ni²⁺ ions in octahedral symmetry. Yet, most Ni²⁺ complexes feature large zero-field splitting, precluding manipulation by commercial microwave sources due to the relatively large spin–orbit coupling constant of Ni²⁺ (630 cm⁻¹). Since low lying excited states also influence axial zero-field splitting, D, a combination of strong field ligands and rigidly held octahedral symmetry can ameliorate these challenges. Towards these ends, we performed a theoretical and computational analysis of the electronic and magnetic structure of a molecular qubit, focusing on the impact of ligand field strength on D. Based on those results, we synthesized 1, [Ni(ttcn)₂](BF₄)₂ (ttcn = 1,4,7-trithiacyclononane), which we computationally predict will have a small D (D_calc = +1.15 cm⁻¹). High-field high-frequency electron paramagnetic resonance (EPR) data yield spin Hamiltonian parameters: g_x = 2.1018(15), g_y = 2.1079(15), g_z = 2.0964(14), D = +0.555(8) cm⁻¹ and E = +0.072(5) cm⁻¹, which confirm the expected weak zero-field splitting. Dilution of 1 in the diamagnetic Zn analogue, [Ni_0.01Zn_0.99(ttcn)₂](BF₄)₂ (1′) led to a slight increase in D to ∼0.9 cm⁻¹. The design criteria in minimizing D in 1 via combined computational and experimental methods demonstrates a path forward for EPR and optical addressability of a general class of S = 1 spins.

A central goal in quantum technologies is to maximize GT₂, where G stands for the coupling of a qubit to control and readout signals and T₂ is the qubit’s coherence time. This is challenging, as increasing G (e.g., by coupling the qubit more strongly to external stimuli) often leads to deleterious effects on T₂. Here, we study the coupling of pure and magnetically diluted crystals of HoW₁₀ magnetic clusters to microwave superconducting coplanar waveguides. Absorption lines give a broadband picture of the magnetic energy level scheme and, in particular, confirm the existence of level anticrossings at equidistant magnetic fields determined by the combination of crystal field and hyperfine interactions. Such “spin clock transitions” are known to shield the electronic spins against magnetic field fluctuations. The analysis of the microwave transmission shows that the spin-photon coupling also becomes maximum at these transitions. The results show that engineering spin-clock states of molecular systems offers a promising strategy to combine sizable spin-photon interactions with a sufficient isolation from unwanted magnetic noise sources.

FSU Quantum initiative has been established to advance university’s research and education in the areas of modern quantum science and technologies.

The mission of the FSU Initiative in Quantum Science and Engineering (FSU Quantum) is to accelerate the discovery of novel quantum phenomena that can impact the design of engineered systems for quantum information processing, communication, sensing, and algorithms, as well as devices and hardware that rely on quantum protocols.

The major goals of FSU Quantum are:

• To operate at the interface between the basic sciences and engineering to ensure advancement of research on quantum science and quantum materials.
• To create a vibrant, open academic program that fosters intra- and inter-institutional research collaborations, educates the future workforce in quantum science and engineering, and disseminates results to society.

Florida State University seeks multiple postdoctoral fellows to join the FSU Quantum Initiative.

Dr. Ferdous Ara is joining the Hill Group as postdoc. She completed Bachelor and Master degree in Physics at Shahjalal University of Science and Technology, Bangladesh. She earned PhD title at Tohoku University, Japan, specializing in molecular spintronics. After completing PhD, she continued research journey as a postdoctoral researcher at Tohoku University, working in the Advanced Scanning Probe Microscopy Laboratory. In this role, the primary focus was on utilizing low-temperature scanning tunneling microscopy (STM) techniques to characterize the electronic and spin states of individual molecules. Subsequently, she joined as a postdoctoral researcher at The Ohio State University, where the work was focused on the development of ESR-STM technology.

Now she joins the Hill Group at National High Magnetic Field Laboratory and The Florida State University, where she will be involved in an Electron Magnetic Resonance project, welcome.

A combination of high-performing lanthanide metallocenes and tetrazine-based radical ligands leads to a new series of radical-bridged dinuclear lanthanide metallocenes; [(Cp*₂Ln^III)₂(bpytz˙⁻)][BPh₄] (where Ln = Gd (1), Tb (2), Dy (3) and Y (4); Cp* = pentamethylcyclopentadienyl; bpytz = 3,6-bis(3,5-dimethyl-pyrazolyl)-1,2,4,5-tetrazine). The formation of the radical species is achieved via a controlled, stepwise synthesis and verified in all complexes by X-ray crystallography and SQUID magnetometry, as well as EPR spectroscopy of 4. Through the judicious choice of the Cp* ancillary ligands and by taking advantage of the steric effects imposed by their bulkiness, we were able to promote the trans coordination mode of the bpytz˙⁻ radical anion that enables stronger magnetic exchange coupling compared to the cis fashion. This yields a J_Gd–rad = −14.0 cm⁻¹ in 1, which is the strongest exchange coupling observed in organic monoanionic radical-bridged lanthanide metallocene systems. The strong Ln-rad exchange coupling was further confirmed by high-frequency EPR (HF-EPR) spectroscopy and broken-symmetry (BS) density functional theory (DFT) calculations. This combined with the highly anisotropic nature of Tb^III and Dy^III ions in 2 and 3, respectively, leads to strong SMM behavior and slow relaxation of the magnetization at zero fields.

Our postdoc Jakub Hrubý will give online talk about “Tunable Clock Transitions in Lanthanide Complexes for Quantum Information Technologies ” at IVEM – EPR seminar on Wednesday, June 21, 9:00 AM EST. Feel free to join the discussion at Zoom: https://fsu.zoom.us/j/91062793719?pwd=QVkrWjh1cVROQ1B5aHNxMnBCT1BRdz09.

Electron Paramagnetic Resonance (EPR) is a powerful technique to study materials and biological samples on an atomic scale. High-field EPR in particular enables extracting very small g-anisotropies in organic radicals and half-filled 3d and 4f metal ions such as Mn^II (3d⁵) or Gd^III (4f⁷), and resolving EPR signals from unpaired spins with very close g-values, both of which provide high-resolution details of the local atomic environment. Before the recent commissioning of the high-homogeneity Series Connected Hybrid magnet (SCH, superconducting + resistive) at the National High Magnetic Field Laboratory (NHMFL), the highest-field, high-resolution EPR spectrometer available was limited to 25 T using a purely resistive “Keck” magnet at the NHMFL. Herein, we report the first EPR experiments performed using the SCH magnet capable of reaching the field of 36 T, corresponding to an EPR frequency of 1 THz for g = 2. The magnet’s intrinsic homogeneity (25 ppm, that is 0.9 mT at 36 T over 1 cm diameter, 1 cm length cylinder) was previously established by NMR. We characterized the magnet’s temporal stability (5 ppm, which is 0.2 mT at 36 T over one-minute, the typical acquisition time) using 2,2-diphenyl-1-picrylhydrazyl (DPPH). This high resolution enables resolving the weak g-anisotropy of 1,3-bis(diphenylene)-2-phenylallyl (BDPA), Δg = 2.5 × 10^–4 obtained from measurements at 932 GHz and 33 T. Subsequently, we recorded EPR spectra at multiple frequencies for two Gd^III complexes with potential applications as spin labels. We demonstrated a significant reduction in line broadening in Gd[DTPA], attributed to second order zero field splitting, and a resolution enhancement of g-tensor anisotropy for Gd[sTPATCN]-SL.