Crystal-field effects in the electron-spin resonance of Gd3+ and Er3+ in Pr2CuO4

The low-temperature (T<300 K) electron-spin-resonance (ESR) spectra of Gd3+ and Er3+ in Pr2CuO4 show symmetry properties appropriate to the crystal tetragonal symmetry. The completely resolved Gd3+ spectra allowed us to measure, at T=2 K, the principal g values g?=1.985(8), g=2.040(8), and the crystal-field parameters [b20=-399(2)×10-4 cm-1, b40=-33.1(7)×10-4 cm-1, and b44=205(3)×10-4 cm-1]. The large broadening of the ESR lines, observed above T40 K, is due to a relaxation via the thermally populated crystal-field excited Pr levels. For Er3+ in Pr2CuO4 we observe a single ESR line corresponding to a ground-state doublet with g?=17.94(5) and g0.2. The absence of any splittings of the ESR lines below the Néel temperature implies that the magnetostatic dipole field at the rare-earth-ion site due to the antiferromagnetically ordered Cu moments is <45 Oe. © 1991 The American Physical Society.