Accurate determination of zero-field splitting using far-infrared magneto-spectroscopy

Far-infrared magneto-spectroscopy (FIRMS) is a valuable experimental tool for exploring the magnetic excitation spectrum within the range of 0.4 to 22 THz (or 12-720 cm^-1). In this presentation, I will detail the FIRMS technique employed at the National High Magnetic Field Laboratory, focusing on its application to single-molecule magnets. A brief overview will cover the measurement protocol, data analysis procedures, and recent advancements in sensitivity. We will also discuss the benefits and constraints of FIRMS in comparison to other spectroscopic methods. Through select examples, we'll highlight how FIRMS can measure zero-field splitting energy and determine spin-Hamiltonian parameters with greater accuracy, especially when integrated with high-frequency EPR data.