Characterizing the spin-polarization of bulk antiferromagnetic tips using single atom magnets

Tips fabricated from bulk antiferromagnets are an attractive material for spin-polarized scanning tunneling microscopy (SP-STM) studies as they provide spin-contrast at zero applied external magnetic field and exhibit a vanishing stray magnetic field. The latter is limiting the investigation of zero field phenomena, such as the study of spin-polarized Majorana modes, Skyrmions, and magnetic bistability in nanomagnets. The characterization and control of these tips is crucial for quantitative studies, yet dependable information regarding the stray magnetic field is scarce. Here, we present a technique for the electrochemical etching of bulk chromium and manganese nickel SP-STM tips from commercially available foils. We describe the in situ preparation and characterization of these tips in an ultra-high vacuum environment using a model system of holmium single atom magnets on a magnesium oxide support.