Monolayer resolved oscillating hyperfine fields in epitaxial face-centered-tetragonal Co(001) films

Area of Science:

• Condensed Matter Physics
• Materials Science
• Surface Science

Background:

• Epitaxial growth of ultrahigh-quality thin films is crucial for understanding interfacial phenomena.
• Cobalt (Co) thin films on copper (Cu)(001) offer a model system for studying magnetism at surfaces and interfaces.
• Nuclear magnetic resonance (NMR) is a sensitive probe of local magnetic environments.

Purpose of the Study:

• To investigate the influence of interfaces on the magnetic properties of ultrahigh-quality face-centered tetragonal (fct) cobalt (Co) films.
• To determine the spatial extent of interface effects on magnetism using monolayer resolution.
• To probe the electronic structure and magnetic interactions at the Co/Cu(001) interface.

Main Methods:

• 59Co nuclear magnetic resonance (NMR) spectroscopy was employed.
• Ultrahigh-quality fct-Co films were grown epitaxially on a Cu(001) substrate.
• Analysis focused on the Co hyperfine field and resonance line characteristics.

Main Results:

• The influence of spin-dependent electron scattering at the interface was observed up to four atomic layers of Co.
• An oscillatory behavior of the Co hyperfine field, with a period of several monolayers, was measured.
• These oscillations are attributed to the oscillating conduction electron polarization.
• The high quality of the Co films, evidenced by narrow NMR resonance lines, enabled these detailed observations.

Conclusions:

• The interface significantly influences the magnetic properties of Co thin films, extending several atomic layers.
• Spin-dependent electron scattering and conduction electron polarization play key roles in interfacial magnetism.
• The exceptional quality of the fct-Co/Cu(001) system is essential for resolving these subtle interfacial effects.