Selective generation of strain waves in optomagnet Fe₂Mo₃O₈

We have previously demonstrated optomagnet effects in antiferromagnetic Fe₂Mo₃O₈ with selective excitations. An energy selection comes from different crystal fields, i.e., Fe²⁺ on octahedral (O-) or tetrahedral (T-) site, while a helicity selection arises from antiferromagnetic ordering. Selective excitations also display drastic differences in time-resolved reflectivity between a magnetic ordered and disordered state when a strain wave forms and propagates into bulk. The strain propagation induces interferences of a probe beam that forms oscillatory signal where amplitudes and initial phases have strong correlations with the magnetic ordering, indicating a potential magnetoelastic coupling. Besides, the magnetic correlation varies between O-site and T-site excitation, implying different couplings originating from the two sites. Our study on selective generation of strain waves will provide innovative technology to the development of spin-acoustic devices.