Crystalline-Field Effects in the EPR of Er in Various Cubic Metals

Electron-spin-resonance measurements on the dilute alloys Ag:Er, Au:Er, Rh:Er, and Ir:Er exhibit a change in slope of the Er-resonance thermal broadening above ∼ 7 K. This behavior is interpreted in terms of off-diagonal matrix elements of the exchange coupling between the ${\Gamma }_7$ ground state and the ${\Gamma }_8^{\mathrm{}\left(1\right)\mathrm{}}$ first-excited state.