Magnetic structure variation in manganese-oxide clusters

Abstract

Negative-ion photoelectron spectroscopy and ab initio simulations are used to study the variation in magnetic structure in MnxOy (x = 3, 4; y = 1, 2) clusters. The ferrimagnetic and antiferromagnetic ground-state structures of MnxOy are 0.16–1.20 eV lower in energy than their ferromagnetic isomers. The presence of oxygen thus stabilizes low-spin isomers relative to the preferred high-spin ordering of bare Mn3 and Mn4. Each cluster has a preferred overall magnetic moment, and no evidence is seen of competing states with different spin multiplicities. However, non-degenerate isomags, which possess the same spin multiplicity but different arrangements of local moments, do contribute additional features and peak broadening in the photoelectron spectra. Proper accounting for all possible isomags is shown to be critical for accurate computational prediction of the spectra.