Spin-polarized Scanning Tunneling Spectroscopy for Imaging the Magnetic Domains of Fe Nano-magnets

Abstract

We report on the recent progress of our study concerning the spin-polarized scanning tunneling spectroscopy (SP-STS). The magnetic states of Fe nano-magnets on W(001) substrates have been investigated. We have observed single-domain and vortex states in the nano-magnets. The micromagnetic simulation well reproduces the magnetic contrast observed in a nano-magnet and demonstrates that the contrast originates from the vortex state in the ground state. The high-resolution magnetic images enable us to experimentally determine the boundary between the single-domain and vortex states. The boundary directly observed with SP-STS is consistent with theoretical predictions. SP-STM with an AC magnetic field for Mn/Fe(001) performed by Wulfhekel et al. is also introduced, indicating that a 180-degree domain wall is formed in the frustrated region in the anti-ferromagnetically coupled Mn layers. Furthermore, the expansion of the domain wall width in the region with increasing the Mn thickness has been obviously observed. Finally, we touch on potentials and remaining issues for industrial application of SP-STS/STM.