ESR of non S state ions in metallic Van Vleck pnictides

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Abstract
The ESR study is reported of Er in PrBi, TmBi and LaBi; Dy in TmBi and PrSb; and Yb in PrSb. The Er ions in these compounds exhibit Gamma 8(1) ground state crystalline field splitting the ground state of Dy and Yb is believed to be a Gamma 6. The resonance properties of the Er in PrBi and TmBi are interpreted in terms of Bleaney's spin Hamiltonian generalized to include the exchange Hamiltonian of Yang et al. (1976). Assuming that the Lea-Leask-Wolf parameter, x, as extracted for the nonmagnetic host LaBi:Er, is identical with those in PrBi:Er and TmBi:Er, the experimental results are consistent with a negligible anisotropic term in the Pr-Er and Tm-Er exchange interactions in these two compounds respectively. This is consistent with the conclusions of Rettori et al. (1975) for PrSb:Er but does not agree with experimental results and theoretical predictions in dilute alloys which indicate significant anisotropic exchange.