New Boundary-Driven Twist States in Systems with Broken Spatial Inversion Symmetry

Area of Science:

• Condensed matter physics
• Materials science
• Magnetism

Background:

• Accurate description of magnetic samples requires proper boundary conditions (BCs).
• Thin film systems are particularly sensitive to boundary properties, which can alter bulk magnetic characteristics.
• Dzyaloshinskii-Moriya interaction (DMI) is a key phenomenon in systems with broken spatial inversion symmetry.

Purpose of the Study:

• To derive general micromagnetic BCs for ferromagnets with DMI.
• To investigate the implications of DMI, particularly its tensorial structure, on magnetic systems.
• To identify novel DMI-induced spin structures in ferromagnetic thin films.

Main Methods:

• Derivation of general micromagnetic BCs for systems with DMI.
• Theoretical analysis of ferromagnets with broken spatial inversion symmetry.
• Focus on systems with C_{∞v} symmetry to explore DMI consequences.

Main Results:

• The derived BCs necessitate the full tensorial structure of the third-rank DMI tensor.
• A purely boundary-driven magnetic twist state is identified at the edges of ferromagnetic thin films.
• This twist state is a new DMI-induced spin structure, independent of the internal DMI field.

Conclusions:

• DMI in thin films leads to unique boundary phenomena not captured by simpler models.
• The magnetic twist state represents a significant new DMI-induced spin texture.
• The associated texture-induced magnetoresistance effect is comparable in magnitude to domain wall effects.