Spin-orbit coupling mode mixing

In contrast to the magnetostriction mechanism the spin-orbit coupling is insensitive to the temperature. Experimentally Ai was observed to disappear very rapidly with raised temperature. At the same time the magnon energy diminished so that the A2 gap appeared at the crossing point of MO and TA modes, but with no appreciable reduction in size. Thus, the mixing of MO-TA and MA-TO modes confirms the importance of spin-orbit coupling in the conduction band states of heavy lanthanides. 

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