M-STM is a vector magnet low-temperature scanning tunneling microscope system. Scanning tunneling microscopy and spectroscopy can be conducted at temperatures down to 375 mK and in magnetic fields up to 9 T in one direction or 2 T in any direction. The STM is placed in a He4 cryostat with an additional He3 circuit. The superconducting coils of the vector magnet surround the STM. Using magnetic tips, spin-polarized tunneling enables us to investigate magnetism at the atomic scale. The very low base-temperature makes tunneling spectroscopy with ultimate energy resolution possible. The system features a load-lock for sample transfer, a versatile preparation chamber for thin film or 2D material growth including initial characterization by low energy electron diffraction, and an exchange chamber to move samples prepared in situ to the STM in the cryostat. Furthermore, samples fabricated elsewhere can be loaded into the system without exposure to atmosphere, by use of a vacuum suitcase at the exchange chamber.
One line of research is the investigation of complex spin structures at surfaces and in thin films. For example, a Bloch-type spin spiral in Fe bilayers on Ir(110) was recently found and characterized by spin-polarized STM. Another line is the investigation of quantum phase transitions in transition metal dichalcogenides. Recently we have investigated self-intercalation and the charge density wave in monolayers of NbS2 on Ir(111).