Perpendicular magnetic anisotropy in a single Dy adatom ferrimagnet

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Chemistry

Background:

• Understanding the electronic structure and magnetism of individual atoms on surfaces is key for developing advanced magnetic materials.
• Ferromagnetic substrates like Ni(111) offer unique platforms for studying surface magnetism.
• Graphene layers can modify the magnetic properties of adsorbed atoms.

Purpose of the Study:

• To investigate the electronic structure and magnetism of individual Dysprosium (Dy) atoms adsorbed on a ferromagnetic graphene/Ni(111) substrate.
• To calculate magnetic moments, magnetic anisotropy energy (MAE), and compare theoretical results with experimental possibilities.
• To resolve ambiguities in conventional density functional theory (DFT+U) applications for rare-earth adatoms.

Main Methods:

• Density Functional Theory with the Hubbard-I approximation to the Anderson impurity model (DFT+U(HIA)).
• Calculation of spin, orbital, and total magnetic moments for the Dy f-shell.
• Computation of X-ray absorption (XAS) and magnetic circular dichroism (XMCD) spectra.
• Determination of magnetic anisotropy energy (MAE) from ground state energy differences.

Main Results:

• A divalent Dy adatom in a specific configuration was identified with significant spin, orbital, and total magnetic moments.
• The Dy f-shell magnetic moments deviate from atomic second Hund's rule.
• Ferromagnetic Ni substrate moments are anti-aligned with the Dy 4f-shell moment.
• A large and positive magnetic anisotropy energy (MAE) of 3.5 meV was calculated, indicating potential for ultra-high density magnetic recording.
• The Dy magnetization tilts due to competing magnetic anisotropy orders.

Conclusions:

• The study provides accurate theoretical predictions for Dy adatoms on graphene/Ni(111), resolving DFT+U ambiguities.
• Calculated magnetic properties, including MAE, are significant for potential applications in magnetic data storage.
• The findings offer a pathway for predicting and designing novel rare-earth-based magnetic nanostructures.