The manifestation of spin-phonon coupling in CaMnO3.

Recently predicted presence of spin-phonon coupling in the CaMnO₃ is experimentally confirmed in infrared (IR), Raman and time-domain THz spectra. Most of phonon frequencies seen below 350 cm^-1 exhibit significant shifts on cooling below antiferromagnetic phase transition at T_N≅120 K. Moreover, several new modes activate in the IR and Raman spectra on cooling below T_N. Sum of phonon contributions to static permittivity exhibits small but reliable anomaly at T_N. On the other hand, the spin-phonon coupling is not manifested in temperature dependence of radio-frequency permittivity, because intrinsic permittivity is screened by extrinsic contribution from conductivity, which enhances the permittivity to giant values. [ABSTRACT FROM AUTHOR]