SP-STM Studies of B20 MnGe

Materials in the B20 crystal structure have broken bulk inversion symmetry, which can lead to the formation of chiral magnetic textures. MnGe is an example with the smallest magnetic period (~3 nm) and largest topological Hall signals observed among B20 chiral magnets. Here, we present spin-polarized scanning tunneling microscopy (SP-STM) characterization of thin MnGe(111) films grown by molecular beam epitaxy. Atomic resolution images show a triangular lattice with a lattice parameter of 6.85 Å in good agreement with the bulk. Three of four possible surface terminations are observed in STM images of different terraces on the surface. Tunneling spectroscopy with a bulk Cr tip shows a pronounced dependence on magnetic field, which we compare to the spin-resolved local density of states calculated by DFT. Counter-intuitively, we observe the largest spin signal from one of the Ge-terminated surfaces, due to their antiferromagnetic coupling to the underlying Mn layer. We also examine magnetic field dependence in topography and spectroscopic maps to probe for surface magnetic structures.