Spin-polarized scanning tunnelling microscopy in magnetic fields

SpSTM - Fig. 1
Superposition of a scanning tunnelling microscopy image of a triangular Co island (bottom) with a measured map of the spin-polarization of the island. We performed spectroscopy measurement in magnetic fields at 7 K to obtain the map of the spin-polarization. The spin-polarization is spatially modulated above the island, and it shows opposite signs at the rim as compared to the center of the island.

Our research focuses on the electronic and magnetic properties of nanostructures with some hundred to several thousand atoms. We use spin-polarized low temperature scanning tunnelling microscopy (STM) and spectroscopy at 7 K and in magnetic fields of up to 8 T to characterize morphology, atomic and spin-dependent electronic structure, and magnetic field dependent transport properties such as tunnel current and differential conductance of individual nanostructures. Our research indicates the significance of spin-dependent quantum effects for the magnetic properties of the nanostructures. We find that in addition to transport properties also the magnetization reversal is influenced by the spatial variation of electronic and structural properties on the nm scale within an individual nanostructure. For detailed description of the method and for a discussion of selected experimental results please consult [1-5]. 

Spin-polarized STM - Movie 1
Electronic and magnetic properties of individual bilayer high Co islands on Cu(111). These islands with a base length of several nm are two atomic layers high and contain several hundred up to several thousand atoms. The image size is 60 nm x 60 nm.
STM - Movie 2
Movie 2: We use scanning tunneling spectroscopy to investigate electron confinement effects in nm small triangular Co islands. The movie reveals a spatial modulation of the spectroscopy signal, which is ascribed to spatial modulations of the local electronic density of states. This movie is measured over a time of several hours, and it is replayed at thousand-fold increased speed.