Electronically Mediated Magnetic Anisotropy in Vibrating Magnetic Molecules.

We address the electronically induced anisotropy field acting on a spin moment in a vibrating magnetic molecule located in the junction between ferromagnetic metals. Under weak coupling between the electrons and molecular vibrations, the nature of the anisotropy can be changed from favoring a high spin (easy-axis) magnetic moment to a low spin (easy plane) by applying a temperature difference or a voltage bias across the junction. For unequal spin polarizations in ferromagnetic metals, it is shown that the character of the anisotropy is essentially determined by the properties of the weaker ferromagnet.