A bulk ring probe made of pure iron wire with diameter of 0.125mm was prepared for spin-polarized scanning tunneling microscopy at room temperature in ultrahigh vacuum. The layerwise antiferromagnetic spin contrast of 2.8 atomic monolayers (ML) Mn/4.5 ML Co/Cu (001) observed with such a probe revealed a spin asymmetry of 14% and a signal-to-noise ratio of 1.8. Areas of reversed spin contrast on the same atomic layer of Mn were observed and attributed to the influence from underlying Co steps and islands. This demonstrates the simplicity of preparation and capability of such bulk Fe ring probes.
