UC Irvine

We have measured the electron-spin-resonance spectrum of Gd3+ ions substituting for Eu ions in Eu2CuO4. The fine structure of the spectrum was partially resolved at room temperature and the individual transitions were completely separated below 100 K. The spectrum is described with a crystal-field effective Hamiltonian of tetragonal symmetry. The values obtained at low temperatures for the corresponding parameters are b20=-486(7)×10-4 cm-1, b40=-32(2)×10-4 cm-1, and |b44|=790(50)×10-4 cm-1. These parameters are only weakly temperature dependent. The measured effective g value is shifted from the free-ion value g=1.992, indicating the existence of antiferromagnetic exchange interactions with the ions of the host. © 1988 The American Physical Society.