We study the magnetically-induced phonon splitting in cubic ACr2O4 (A=Mg, Zn, Cd, Hg) spinels from first principles, and demonstrate that the sign of the splitting, which is experimentally observed to be opposite in CdCr2O4 compared to ZnCr2O4 and MgCr2O4, is determined solely by the particular magnetic ordering pattern observed in these compounds. We further show that this interaction between magnetism and phonon frequencies can be fully described by the previously proposed spin-phonon coupling model that includes only the nearest neighbor exchange. Finally, using this model with materials specific parameters calculated from first principles, we provide additional insights into the physics of spin-phonon coupling in this intriguing family of compounds.
@article{arxiv.1508.00834,
title = {Magnetically induced phonon splitting in ACr$_2$O$_4$ spinels from first principles},
author = {Aleksander L. Wysocki and Turan Birol},
journal= {arXiv preprint arXiv:1508.00834},
year = {2016}
}