Nano-Magnetic Probing on Magnetite

We report our results on the structure and magnetic imaging of Fe ₃O₄ (110) thin films using scanning tunneling microscopy/spectroscopy (STM/STS). Based on atomically resolved STM images we present a model for the observed ridge reconstruction of the surface, in agreement with a bulk-truncated layer containing both octahedral and tetrahedral iron ions. The weak contrast between the tops and the valleys of the ridges in the current map measured with W tips is attributed to the tetrahedral and octahedral character, respectively. We observe a contrast enhancement at the W tip change accompanied by a corrugation enhancement. An antiferromagnetic MnNi tip detects a large contrast between tops and valleys in the current map and two surprising states, at 0.3-V and -0.7-V bias voltages. We attribute the observed contrast to magnetism in agreement with our proposed model