Anisotropic spin-Peierls state in the inorganic compoundM. Miljak1, M. Herak1, A. Revcolevschi2 and G. Dhalenne2
1 Institute of Physics - Bijenicka c. 46, 10000 Zagreb, Croatia
2 Laboratoire de Phisico-Chimie de l'Etat Solide, Université de Paris Sud Bâtiment 414, 91405 Orsay, France
received 6 July 2004; accepted in final form 15 March 2005
published online 13 April 2005
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 an anisotropic exponent. This is, to our knowledge, the first observation of the anisotropic exponent . 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 . iv) The paramagnetic defects causing a low-temperature susceptibility upturn are ions, but of different oxygen surroundings than the rest of the moments.
75.30.Gw - Magnetic anisotropy.
75.30.Hx - Magnetic impurity interactions.
75.30.Et - Exchange and superexchange interactions.
© EDP Sciences 2005