Magnetic circular dichroism spectroscopy on the Cr8 antiferromagnetic ring

A Magnetic Circular Dichroism (MCD) spectroscopic study of the antiferromagnetic ring [Cr8F8Piv16] (Piv = pivalate) is reported. From the splitting of the MCD bands, the single ion anisotropy parameters in the cluster spin ground state at different fields were determined to be dCr = −0.33 ± 0.02 cm−1, eCr = 0.11 ± 0.01 cm−1. Analysis of the MCD intensity as a function of field and temperature revealed the influence of spin mixing effects and yielded independent estimates of the single ion anisotropies (dCr = −0.19 cm−1, eCr = 4.3 × 10−4 cm−1), as well as yielding the isotropic exchange interaction strength (J = −6.00 cm−1). Thus it is shown that MCD is a powerful method to unravel the relation between single-ion and cluster anisotropy, furthering the design of molecular magnets with desired properties.