Electron paramagnetic resonance (EPR) in single crystals of gadolinium metal has been studied near its Curie temperature $T_C \left(\simeq 293 \mathrm{K}\right)$. The EPR linewidth $\Delta H$ and the resonance field $H_r$ are measured as a function of temperature between 280 and 330 K, for $\overrightarrow{\mathrm{H}}\parallel c$ axis and $\overrightarrow{\mathrm{H}}\perp c$ axis. Between 300 and 330 K the line shape is Dysonian and $\Delta H$ shows a crossover behavior: i.e., $\Delta H$ increases as $T\to T_C^{+}$, reaching a maximum at $T_m>T_C$ and then decreases for lower temperatures. This behavior of $\Delta H$ is similar to the observations in ferromagnets Cr${\mathrm{Br}}_3$, EuO, and Ni. The derived values for the critical spin-spin relaxation rate in Gd are observed to scale as ${\chi }^{\nu }$, where $\chi$ is the uniform field susceptibility. The observed value of $\nu \simeq 0.84$ is about half the theoretical value, similar to the discrepancy observed in antiferromagnets.

• Received 15 April 1977

DOI:https://doi.org/10.1103/PhysRevB.16.1802