Anisotropic spin-Peierls state in the inorganic compound

¹ Institute of Physics - Bijenička c. 46, 10000 Zagreb, Croatia
² Laboratoire de Phisico-Chimie de l'Etat Solide, Université de Paris Sud Bâtiment 414, 91405 Orsay, France

Corresponding author: mirta@ifs.hr

Received: 6 July 2004
Accepted: 15 March 2005

Abstract

The static susceptibility and susceptibility anisotropy of the single-crystalline were measured. Combined results of both techniques reveal the following experimental facts: i) The low-temperature susceptibility upturn obeys a power law temperature dependence of the form with α an anisotropic exponent. This is, to our knowledge, the first observation of the anisotropic exponent α. ii) In the paramagnetic region above the spin-Peierls transition temperature the measurements reveal the anisotropic and temperature-dependent exchange interaction, J. iii) The anisotropic exchange interaction results in the anisotropy of the excitation energy gap Δ. iv) The paramagnetic defects causing a low-temperature susceptibility upturn are ions, but of different oxygen surroundings than the rest of the moments.