Search for magnon-phonon coupling effect in metallic triangular antiferromagnet CrB2

Spin dynamics of non-collinear magnetic structures can exhibit the rare phenomena which go beyond the linear spin wave theory. Our previous studies on non-collinear antiferromagnetic insulators (Y, Lu)MnO3 at ISIS showed that magnon-magnon/phonon interactions indeed have a sizable effect on the spin dynamics. To extend this concept to metallic systems, we have recently carried out an inelastic neutron scattering experiment at MAPS on CrB2, a metallic triangular antiferromagnet with non-collinear magnetic structure. Along with successful measurements of magnons over a large momentum-energy space, we observed that some phonon modes near the magnon modes have unusual behavior, which is also seen in (Y, Lu)MnO3. To confirm that this anomaly comes from magnon-phonon coupling, we propose to investigate the phonon spectra of CrB2 at 150 K, the temperature above TN =88 K where magnons disappear.