Interplay of dipolar and random strain effects in the cooperative Jahn-Teller system TmAsO₄

Electron paramagnetic resonance studies of the cooperative Jahn-Teller system TmAsO4 doped with Gd show that above ∼ 140 K dynamic random strains caused by the strong interaction of the first excited electronic doublet of Tm3+ with phonons are the major mechanisms for the line broadenings. At lower temperatures, because of the weaker interactions of the ground electronic doublet with the phonons, the induced dipolar mechanism for the line broadenings becomes important. © 1977.