Understanding the elusive magnetic behavior of manganese clusters

Manganese is a multifarious element and presents a large variety of behaviors. With the aim of understanding the complex behavior, we performed a systematic study of the magnetic solutions of the manganese dimer as a function of the interatomic distance. The calculation is performed within the framework of an ab initio calculation. We show that a remarkable interplay between different magnetic couplings leads to a transition between antiferromagnetic and ferromagnetic couplings as a function of interatomic distance. We present the electronic spectra for the two configurations for different interatomic distances and show clearly the role of the $4s$ to $3d$ electron transfer to stabilize the antiferromagnetic solution at short distances. Our results are in good agreement with experiment.