Raman scattering studies of spin-waves in hexagonal BaFe12O19


Xiang-Bai Chen, Department of Nano Science & Mechanical Engineering and Nanotechnology Research Center, Konkuk University, Chungju 380-701, Korea. E-mail: xchen@kku.ac.kr

In-SangYang, Department of Physics and Division of Nano-Sciences, Ewha Womans University, Seoul 120-750, Korea. E-mail: yang@ewha.ac.kr


We present the results of polarized Raman spectroscopy of hexagonal BaFe12O19 single crystal. The spectra, recorded from 200 to 800 cm–1 and 1100 to 1700 cm–1 in the 20–250 K temperature range, are analyzed on the basis of both crystal vibrations and spin-waves. In the low wavenumber range, the Γ-point phonons are observed. In the high wavenumber range, phonon mixings are observed; more interestingly, four modes of spin-waves are identified in hexagonal BaFe12O19. Both have not been studied previously. Our analyses of the spin-waves provide an optical method for quantitatively estimating the spin exchange interactions in hexagonal BaFe12O19. The four strong exchange integrals are found to have the values of Jce = 1.31 meV, Jae = 1.36 meV, Jcd = 1.46 meV, and Jbd = 1.71 meV. Our results also indicate that at ~200 and ~80 K, there would be additional spin-ordering transitions in hexagonal BaFe12O19. Copyright © 2012 John Wiley & Sons, Ltd.