Optical evidence for a magnetically driven structural transition in the spin web

¹ Laboratorium für Festkörperphysik, ETH Zürich - CH-8093 Zürich, Switzerland
² Institut de Physique de la Matière Complexe (IPMC), EPF Lausanne CH-1015 Lausanne, Switzerland

Received: 30 November 2005
Accepted: 9 June 2006

Abstract

Cu₃TeO₆ is a modest frustrated spin system, which undergoes an antiferromagnetic transition at K. The antiferromagnetic spin alignment in Cu₃TeO₆ below T_N is supposed to induce a magneto-elastic strain of the lattice. The complete absorption spectrum of Cu₃TeO₆ is obtained through Kramers-Kronig transformation of the optical reflectivity, measured from the far-infrared up to the ultraviolet spectral range as a function of temperature (T). Below K, we find a new mode at 208 cm^-1. The spectral weight associated to this additional mode increases as with decreasing T below T^*. The implication of the optical findings will be discussed in relation to the magnetic phase transition at T_N.