Abstract
The energy spectrum of magnons propagating along the [001] and [110] directions in ferromagnetic dysprosium at 4.7° and 78°K has been determined by triple‐axis neutron spectrometry. Throughout this temperature range the measured energy gap at zero wave vector (q⇒ ⇒ 0) is approximately 40% larger than that calculated from the macroscopic magnetostriction and crystal‐field anisotropy constants. Although the magnon energies increase with decreasing temperature, the variation near q⇒ = 0 is much stronger than that near the Brillouin zone boundaries. Thus, the magnitude of the exchange interaction decreases substantially, ∼25% in the c‐direction, between 78° and 4.7°K. Significant magnon‐phonon interactions are observed, particularly in the [110] direction where the acoustic magnon branch appears to be mixed with both the longitudinal and transverse acoustic phonon branches.
Published Version
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