A synergistic approach combining the experimental photoelectron spectroscopy and theoretical electronic structure studies is used to demonstrate the existence of magnetic isomers as well as configurations having comparable binding energies, identical spins, and yet differing in the distribution of local moments (called isomags). Our studies carried out on ${\mathrm{Mn}}_5\mathrm{O}$ and ${\mathrm{Mn}}_6\mathrm{O}$ clusters show that while the $\mathrm{O}$ atom occupies either bridge or hollow site with a binding energy of $6.88\mathrm{eV}$ in ${\mathrm{Mn}}_5$, it prefers a hollow site with a binding energy of $7.18\mathrm{eV}$ in ${\mathrm{Mn}}_6$ clusters. ${\mathrm{Mn}}_5\mathrm{O}$ is shown to possess two magnetic isomers with total spins of 13 and $5{\mu }_{\mathrm{B}}$ that contain three and five isomags, respectively. ${\mathrm{Mn}}_6\mathrm{O}$ possesses three isomers, two with moments of 8 and $2{\mu }_{\mathrm{B}}$ and a nonmagnetic. It is shown that the isomags, although undetected in magnetic experiments, can be identified via their electronic structure in experimental photoelectron spectra.

• Received 15 March 2004

DOI:https://doi.org/10.1103/PhysRevB.70.134422