Ab initio investigation of the role of the bridging atoms to the spin transferability between magnetic centrers

• Applicant: Professor Dr. Wolfgang Hübner
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2013 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 233527043

While magnetic disks are gradually being replaced by nonmagnetic means of storing information (flash rams, solid state disks, SSD) there is an ongoing strive to replace other computer parts, traditionally nonmagnetic, by magnetic counterparts. At the same time the miniaturization of (electronic) circuits down to an atomic level has become a most desirable industrial goal. These two reasons combined have led to an increase of both the theoretical and experimental investigation of spintronic devices and coherent manipulation of the magnetic state of nanostructures.The goals of the first two-year period of the current project were to investigate how the electronic bridging of adjacent magnetic centers (here Fe, Co, Ni atoms) affects the spin transferability and thus the logic functional operability of multicenter magnetic molecules. This included the investigation of spin transfer as a function of the chemical nature (metallicity), the number, and the spin and charge polarization of the bridging atoms.When pursuing those goals we derived several mechanisms both for spin flip and for spin transfer, as well as many general rules which govern them. However, these general rules seem to rely mostly on geometrical grounds instead of the chemical nature of the bridge atoms. At present we understand that the symmetry of a cluster needs to be sufficiently low and the energetic difference between initial/final state and intermediate state(s) has to be sufficient high to ensure a successful Lambda-process. During the investigation we came to some additional remarkable results. In detail we have found that a substantial mechanism is the phonon-spin coupling which acts as a mediator for our optically driven processes. This motivates the more detailed study of (i) the role metallicity of the bridging atoms, (ii) the effect of phonon-spin coupling, (iii) the role of the electronic states on the indirect phonon-spin coupling, and (iv) the effect of CO including phonons on the spin dynamic processes.Elucidating further those mechanisms will ease the targeted designing of even more successful nanostructures, and thus substantially contribute to the development of functional, nanoscale magnetic devices.

• DFG Programme: Research Grants
• Participating Person: Dr. Georg Lefkidis