ELFT HÍRADÓ

[udvardi AT bolyai.phy.bme.hu (Udvardi Laszlo)]

                                 MEGH'IV'O
               A Budapesti Muszaki Egyetem, Fizikai Int'ezet
                    Elm'eleti Fizika Tansz'ek tudom'anyos
                              szemin'arium'ara

                                   T'ema:
      Kondo effect and STM spectra through ferromagnetic nanoclusters

                                  El"oad'o:

                                 Greg Fiete 
             Harvard University, USA


            Id"opont: 2002. november 15.-'en  10.15 'ora

   Hely :     Budafoki 'ut 8 (F-'ep"ulet, III. lh., mfsz.,
                      Szemin'ariumi szoba

            Minden 'erdekl"od"ot sz'i vesen l'atunk !


                        Udvardi La'szlo'


Abstarct:
---------
 Motivated by recent scanning tunneling microscope (STM) experiments on
cobalt clusters adsorbed on single-wall metallic nanotubes [Odom et al.,
Science 290, 1549 (2000)], we study theoretically the size dependence of
STM spectra and spin-flip scattering of electrons from finite size
ferromagnetic clusters adsorbed on metallic surfaces. The effective
exchange coupling between the spin of the cluster and the conduction
electrons of the metallic substrate depends on the specific details of the
single-particle density of states on the cluster. The calculated Kondo
coupling is inversely proportional to the total spin of the ferromagnetic
cluster in both models and thus the Kondo temperature is rapidly
suppressed as the size of the cluster increases. Mesoscopic fluctuations
in the charging energies and magnetization of nanoclusters can lead to
large fluctuations in the Kondo temperatures and a very asymmetric voltage
dependence of the STM spectra. We compare our results to the experiments.