Benchmarking Cantilever Torque Magnetometry as a Platform for Characterizing Molecular Qubits: A Case Study on Ni(II)...

Area of Science:

• Quantum Information Science
• Materials Science
• Condensed Matter Physics

Background:

• Determining the electronic structure of transition metal complexes is crucial for developing molecular qubits.
• Current methods for characterizing spin Hamiltonian parameters often require large facilities or extensive sample quantities.
• Limited spectral access and sensitivity to anisotropies hinder precise characterization of leading qubit candidates.

Purpose of the Study:

• To demonstrate cantilever torque magnetometry (CTM) as a sensitive, accessible method for characterizing spin systems.
• To enable precise determination of spin Hamiltonian parameters from microgram-scale single crystals.
• To decouple and precisely measure g-tensor anisotropy and zero-field splitting (ZFS) using CTM.

Main Methods:

• Utilized cantilever torque magnetometry (CTM) for high-sensitivity magnetic anisotropy measurements.
• Exploited distinct temperature dependences of g-tensor anisotropy and zero-field splitting (ZFS) for experimental decoupling.
• Analyzed microgram-scale single crystals of transition metal complexes.

Main Results:

• CTM achieved high sensitivity to magnetic anisotropy with minimal sample demands and laboratory-scale accessibility.
• Precisely determined bulk-mean values of spin Hamiltonian parameters by decoupling g-tensor anisotropy and ZFS.
• CTM-derived parameters showed qualitative consistency but quantitative differences (∼1% for g, ∼5-15% for ZFS) compared to high-frequency electron paramagnetic resonance spectroscopy.

Conclusions:

• CTM is a powerful, broadly accessible technique for characterizing molecular spin systems.
• It serves as a valuable complement to magnetic resonance methods in quantum information science.
• CTM opens new avenues for high-precision characterization of low-anisotropy spin systems.