ESR of Gd3+ in magnetically ordered Eu2CuO4

Abstract

Electron spin resonance (ESR) experiments of ${\mathrm{Gd}}^{3+}$ in the antiferromagnetic (AF) ordered phase (T<${\mathit{T}}_{\mathit{N}}$) of ${\mathrm{Eu}}_2$ ${\mathrm{CuO}}_4$ can be interpreted in terms of four magnetically nonequivalent rare-earth sites with local internal fields ${\mathit{H}}_{\mathit{i}}$=±310(30) Oe along the [100] and [010] directions. The internal field is well described by a dipolar magnetic field of a noncollinear AF array of 0.35(4) ${\mathrm{\mu }}_{\mathit{B}}$ per Cu moment aligned along the [100] and [010] directions. This is consistent with recent results of magnetic-field-dependent neutron-diffraction experiments. From the ESR and magnetic susceptibility data, the crystal field parameters for ${\mathrm{Gd}}^{3+}$ and ${\mathrm{Eu}}^{3+}$ in ${\mathrm{Eu}}_2$ ${\mathrm{CuO}}_4$ are determined. The exchange parameters between the rare earths are also estimated. © 1996 The American Physical Society.