We study the magnetically-induced phonon splitting in cubic ACr2O4 (A=Mg, Zn, Cd) 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 [C. J. Fennie and K. M. Rabe, Phys. Rev. Lett. 96, 205505 (2006)]PRLTAO0031-900710.1103/PhysRevLett.96.205505 that includes only the nearest neighbor exchange. 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.
Bibliographical noteFunding Information:
We acknowledge fruitful discussions with Craig J. Fennie and Karin Rabe. Work at Ames Lab was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences, Materials Science and Engineering Division. Ames Laboratory is operated for the U.S. DOE by Iowa State University under Contract No. DE-AC02-07CH11358. T.B. was supported by the Rutgers Center for Materials Theory.