Controlling the magnetization direction in molecules via their oxidation state

By means of ab initio calculations we predict that it is possible to manipulate the magnetization direction in organic magnetic molecules by changing their oxidation state. We demonstrate this novel effect on the Eu-2(C8H8)(3) molecule, in which the hybridization of the outer pi ring states with the Eu 4f states causes a redistribution of the orbitals around the Fermi level leading to a strong ferromagnetism due to a hole-mediated exchange mechanism. As a key result, we predict an oscillatory behavior of the easy axis of the magnetization as a function of the oxidation state of the molecule-a new effect, which could lead to new technological applications.