Two-magnon Raman scattering from the Cu3O4 layers in (Sr,Ba)2Cu3O4Cl2

J. Holmlund; C. S. Knee; J. Andreasson; M. Granath; A. P. Litvinchuk; L. Borjesson

doi:10.1103/PhysRevB.79.085109

paper

Two-magnon Raman scattering from the Cu3O4 layers in (Sr,Ba)2Cu3O4Cl2

arXiv:0804.1859 · doi:10.1103/PhysRevB.79.085109

Abstract

(Sr $_{2}$ ,Ba $_{2}$ )Cu $_{3}$ O $_{4}$ Cl $_{2}$ are antiferromagnetic insulators which are akin to the parent compounds of the cuprate superconductors but with two distinct magnetic ordering temperatures related to two magnetic Cu $_{I}$ and Cu $_{I I}$ spin sublattices. Here we present a study of these materials by means of Raman spectroscopy. Following the temperature and polarization dependence of the data we readily identify two distinct features at around 3000 cm $^{- 1}$ and 300 cm $^{- 1}$ that are related to two-magnon scattering from the two sublattices. The estimated spin-exchange coupling constants for the Cu $_{I}$ and Cu $_{I I}$ sublattices are found to be J $_{I} \sim$ 139-143(132-136) meV and J $_{I I} \sim$ 14(11) meV for Sr(Ba) compounds. Moreover, we observe modes at around 480 and 445 cm $^{- 1}$ for the Sr and Ba containing samples respectively, that disappears at the ordering temperature of the Cu $_{I I}$ . We argue that this modes may also be of magnetic origin and possibly related to interband transitions between the Cu $_{I}$ -Cu $_{I I}$ sublattices.

7 pages, 8 figures