Density functional study of the magnetic properties of Bi₄Mn clusters: Discrepancy between theory and experiment

We have performed collinear and non collinear calculations on neutral Bi4Mn, and collinear ones on ionized Bi4Mn with charges +1 and -1 to find out why theoretical calculations will not predict the magnetic state found in the experiment. We have used the density functional theory to find a fit between the theoretical prediction of the magnetic moment with the experimental value. Our calculations have consisted in a structure search of local energy minima, and then a search of the magnetic lowest energy state for each resulting isomer. The geometry optimization found 3 local minima whose fundamental state is the doublet spin state, which could not be found in previous theoretical works, but they are higher in energy than the lowest-lying isomer by approximately 1.75 eV. This magnetic state could help understand the experiment. Calculations of non-collinear magnetic states for the Bi4Mn do not lower the total magnetic moment. We conclude arguing how the 3 isomers with doublet state could actually be the ones measured in the experiment.