Investigation of magnetically frustated spin chains on ferromagnetic substrates by spin-polarized STM
Simon Holzberger, KIT, Karlsruhe (Institut für Physik) (Einladung zum SFB-TRR 49 Kolloquium)

Abstract:
A novel even-odd effect is theoretically predicted for monoatomic manganese chains on a ferromagnetic Ni(100) surface by S. Lounis et al.
[1]. This effect is a consequence of the inherent magnetic frustration of the antiferromagnetic chain on the ferromagnetic surface. To investigate these nanochains experimentally, low-temperature spin-polarized scanning tunneling microscopy with its high special resolution is ideally suited.
To favor the growth of nanochains we chose a ferromagnetic Ni(110) surface. However, it is impossible to grow pure manganese chains on Ni(110) by self-assembly, thus the chains were created by atomic manipulation. The electronic structure of the so formed short chains was investigated by non-magnetic scanning tunneling spectroscopy (STS). The revealed electronic structure is strongly dependent on the length of the chain and can be explained within the model of an unoccupied quasi atomic state in single manganese adatoms. In order to obtain the magnetic structure of the frustrated manganese nanochains, we use the spin-polarized STS mode. In agreement with the theoretically prediction for the system Mn/Ni(100), we found a collinear antiferromagnetic ground state for linear manganese trimers. In contrast to the calculations,there was no indication of an antiferromagnetic or non-collinear spin structure for even-numbered chains. This observation could be related to degenerated ground states.
[1] S. Lounis et al., Phys. Rev. Lett. 101, 107204 (2008)