Momentum-Dependent Magnon Lifetime in the Metallic Noncollinear Triangular Antiferromagnet CrB_{2}

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Magnetism

Background:

• Noncollinear magnetic order is prevalent in magnetic systems, influencing spin dynamics.
• Understanding magnon decay in metallic magnets with noncollinear order remains a challenge.
• Linear spin wave theory often fails to explain observed phenomena in complex magnetic systems.

Purpose of the Study:

• To investigate the spin dynamics and magnon decay mechanisms in the metallic noncollinear antiferromagnet CrB2.
• To elucidate the contributions of two-magnon decay and the Stoner continuum to magnon damping.
• To provide experimental evidence for higher-order effects in metallic antiferromagnets.

Main Methods:

• Inelastic neutron scattering was employed to probe the magnetic excitation spectra of CrB2.
• Analysis of magnon linewidth (Γ(q,Eq)) as a function of momentum (q) and energy (Eq).
• Comparison of experimental data with theoretical predictions, including two-magnon decay and Stoner continuum models.

Main Results:

• Observed intrinsic magnon damping and continuumlike excitations not predicted by linear spin wave theory.
• Unusual momentum dependence of the intrinsic magnon linewidth was identified.
• The interplay between two-magnon decay and the Stoner continuum was found to govern magnon damping.

Conclusions:

• The study provides a rare, comprehensive analysis of spin dynamics in metallic noncollinear antiferromagnets.
• Definitive experimental evidence for higher-order effects influencing magnon decay in these materials is presented.
• The findings advance the understanding of fundamental magnetic interactions and quasiparticle behavior in complex magnets.