Antiferromagnetic resonance in EuTe

Previous measurements of the low-frequency branch of the "easy-plane" antiferromagnet have been extended to the high-frequency branch. The resonance fields as a function of angle at constant frequencies greater and less than the zero-field resonance frequency, ${\omega }_c$, have been measured and analyzed based on resonance equations including the dipolar and a phenomenological uniaxial anisotropy energy. Good agreement is obtained for branches associated with the different $T$ domains. Deviations, attributed to domain-wall effects, are observed. The zero-field resonance frequency, ${\omega }_c$, has been determined from measurements of $\omega$ vs $H$ with $\overrightarrow{\mathrm{H}}$ in an easy plane. The decrease in ${\omega }_c\mathrm{}\left(T\right)\mathrm{}$ with increasing temperature is proportional to $T^{\frac{3}{2}}$ and is the same as found for the critical (exchange) field by Oliveira et al. The frequency ${\omega }_c$ at $T=0\mathrm{}$ corrected for demagnetizing effects corresponds to a dipolar interaction, $K_d=0.817\mathrm{}\times {10}^6$ erg/${\mathrm{cm}}^3$, which is ∼10% larger than the classically calculated value for EuTe. The exchange field, $H_E$, determined from the variation $\omega$ vs $H$ with $\overrightarrow{\mathrm{H}}$ in an easy plane was obtained. The value at $T=0\mathrm{}$ and corrected for demagnetizing effects is $H_E\mathrm{}\left(0\right)=73.0\mathrm{}$ kOe compared with the value $H_E=72.2\mathrm{}$ kOe determined directly by Oliveira et al. This excellent agreement is considered fortuitous.