Phono-magnetic analogs to opto-magnetic effects*

Remote control of magnetic order can be achieved through opto-magnetic effects, such as the inverse Faraday and inverse Cotton-Mouton effects. Here, we theoretically describe phonon analogs of these effects, in which coherently excited infrared-active phonons replace photons in the scattering process, which is mediated through spin-phonon coupling. We compare the strengths of the opto- and phono-magnetic effects in antiferromagnetic NiO, in which we find them to generate comparable magnitudes of effective magnetic fields acting on the spins. We further investigate the phonon inverse Faraday effect in paramagnetic CeCl₃, in which extraordinarily strong spin-phonon coupling has been observed. We predict that giant effective magnetic fields of up to 100 T that align the paramagnetic spins can possibly be generated through coherent phonon excitation with experimentally achievable pulse strengths. Our results show that phono-magnetic effects emerge as promising tools for ultrafast spin control at terahertz frequencies.