Antiferromagnetic-Resonance Measurements in Europium Telluride

Abstract

EuTe is a fcc antiferromagnet with ordering of the second kind. Antiferromagnetic-resonance measurements on single crystals have been performed as a function of crystallographic orientation at 1.17\ifmmode^\circ\else\textdegree\fi{}K and at the frequencies 9, 18, and 24 GHz. The results show that the dominant anisotropy energy contribution is of dipolar origin and that the sublattice magnetization vectors lie in {111} planes. There is, in addition, a weak anisotropy in the (111) plane which make the $〈11\overline{2}〉$ or equivalent directions the zero-field easy axes. The values of the dipolar and in-plane anisotropy fields are 4000 and 8 G, respectively. For this "easyplane" behavior, the two resonant branches are nondegenerate in zero field and have the values 2 and 68 GHz. The behavior of the spin-flop transition with the magnetic field along an in-plane easy axis has been examined. The energy change associated with this transition is calculated to be $\ensuremath{\Delta}E=[8+{(\frac{3{H}_{f}}{2{H}_{E}})}^{2}]{K}_{2}$, where ${K}_{2}$ is the in-plane anisotropy energy, ${H}_{f}$ the spin-flop field, and ${H}_{E}$ the exchange field.