INDIRECT IMPURITY AND HOST MODE EXCITATION VIA FAR-INFRARED LEVEL-CROSSING SPECTROSCOPY IN ANTIFERROMAGNETS

Through the field dependence of its linewidth, the s0 local mode at 83 cm-1 associated with a V2+ impurity in FeF2 is used as a novel probe of impurity shell modes, host magnon density of states, and the phonon mixing of the magnon branches at the magnonacoustic-phonon level crossings. This is the first observation of individual shell modes. Sz-nonconserving and direct exchange interactions contribute to the s0-local-mode relaxation. The method has general applicability to antiferromagnets. © 1990 The American Physical Society.