Magnetic force microscopy on nanocrystalline Co films.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Magnetism

Background:

• Perpendicular magnetic domains in ultrathin films arise from interface anisotropy.
• Tetragonal distortion can induce perpendicular domains via magnetoelastic anisotropy.
• Epitaxial hexagonal close-packed (hcp) cobalt films exhibit perpendicular stripe domains due to bulk magnetocrystalline anisotropy.

Purpose of the Study:

• To investigate the influence of sputtering conditions on the structure and magnetic domain configuration of cobalt films.
• To explore the relationship between film texture and the formation of perpendicular magnetic domains.
• To understand the role of different crystal structures (hcp, fcc, amorphous) in magnetic domain formation.

Main Methods:

• Radio frequency magnetron sputtering of cobalt films with thicknesses ranging from 15 to 4500 nm.
• Utilized various substrates including Corning glass, silicon, and aluminum foil at a substrate temperature of 350 K.
• Characterized film structure and texture using X-ray diffraction experiments, analyzing the impact of Ar-pressure and deposition rate.

Main Results:

• Cobalt films exhibited diverse structures and textures dependent on preparation conditions (Ar-pressure, deposition rate).
• Stripe-like and labyrinth-like magnetic domain configurations were observed in films textured along the c-axis and in films with mixed hcp/fcc grains, respectively.
• Films with predominantly fcc or amorphous structures did not form perpendicular magnetic domains.

Conclusions:

• Film texture, particularly c-axis orientation and the presence of hcp grains, is crucial for forming perpendicular magnetic domains in sputtered cobalt films.
• The observed domain configurations correlate with the underlying crystallographic structure and texture.
• Magnetization loops provide insights into the magnetic properties related to the observed domain structures.