Spin-polarized scanning tunneling microscopy with antiferromagnetic probe tips

Area of Science:

• Surface science
• Condensed matter physics
• Materials science

Background:

• Spin-polarized scanning tunneling microscopy (SP-STM) is crucial for nanoscale magnetic imaging.
• Investigating magnetic thin films like iron on tungsten (Fe/W(110)) presents challenges with ferromagnetic probe tips.
• Existing methods can be limited by the probe's own magnetic field, affecting measurements of soft or superparamagnetic materials.

Purpose of the Study:

• To develop an improved SP-STM technique for high-resolution magnetic imaging.
• To investigate the magnetic domain structure of iron thin films on a W(110) substrate.
• To assess the utility of antiferromagnetic probe tips in overcoming limitations of ferromagnetic tips.

Main Methods:

• Low-temperature SP-STM was employed to study two monolayers of Fe on W(110).
• Tungsten tips were coated with different magnetic materials, including chromium (Cr).
• SP-STM imaging was performed with both ferromagnetic and antiferromagnetic (Cr-coated) probe tips, including in the presence of external magnetic fields.

Main Results:

• Stripe magnetic domains were observed with a characteristic period of 50 +/- 5 nm.
• SP-STM imaging using a Cr-coated antiferromagnetic tip yielded clear images.
• The vanishing dipole field of the Cr tip minimized interference, particularly in external magnetic fields.

Conclusions:

• Antiferromagnetic probe tips, specifically Cr-coated ones, offer a significant advantage in SP-STM.
• This approach effectively resolves the issue of disturbing tip-sample magnetic interactions.
• The developed method enhances the investigation of sensitive magnetic materials like soft magnets and superparamagnetic particles.