Torque-detected ESR of a Tetrairon(III) Single Molecule Magnet

Single-crystal studies on anisotropic ESR-active materials can be conveniently carried out using torque-detected (TD) ESR, a novel technique which brings to ESR the sensitivity typical of torque magnetometry (TM). This method, which is easily operated in high magnetic fields and in a wide range of frequencies, was applied to investigate magnetic anisotropy in crystals of a tetrairon(III) single-molecule magnet with an S = 5 ground state. TDESR was supported by TM measurements carried out in situ and provided an accurate estimate of the second-order axial anisotropy parameter D and of the longitudinal fourth-order contribution B40. The results were validated through a parallel angle-resolved investigation by traditional high-frequency ESR on the same material.