Electronic Raman studies of antiferromagnetic dysprosium aluminum garnet below TN and with and without an applied magnetic field

Abstract

Electronic Raman transitions within the H1526 and to the H1326 manifolds of antiferromagnetic dysprosium aluminum garnet (DyAlG) at 1.5 K (TN=2.5K) have been observed. Comparison of the Raman spectra obtained when a magnetic field (18 kOe) was applied along the [001] direction and when Happ=0 yielded estimations for the following: (a) the internal field splittings and consequently the exchange fields of the first two excited Kramers doublets in H1526; and (b) the Zeeman splittings of these levels. Using wave functions from our crystal-field analysis (Wadsack et al.), the g values of all the levels in the H1526 and H1326 manifolds have been calculated. These compared well with the g values previously observed (Aoyagi et al.) and with our Raman determination of gz=14.7±1 for the lowest level in H1326. Contributions to the electronic Raman scattering tensors from the six magnetic sublattices were derived for the applied field along [001] and for the different combinations of incident and scattered polarizations. Using the crystal-field wave functions for DyAlG, the relative Raman intensities for the observed Raman transitions were calculated. These Raman intensities are as sensitive to the crystal-field wave functions as are the g values. The calculated and observed Raman intensity ratios for various polarization combinations agreed only qualitatively. Breakdown of phonon polarization selection rules for the Eg and A1g, but not the T2g Raman-active phonons, was observed when Happ=18kOe. No explanation was given for this observation. © 1971 The American Physical Society.