Temperature evolution of structural and magnetic properties of stoichiometric LiCu_2O_2: Correlation of thermal expansion coefficient and magnetic order

摘要

Temperature-dependent crystallographic and magnetic studies on stoichiometric single crystals of LiCu_2O_2 are reported. The temperature dependence of the lattice parameters was extracted from X-ray powder diffractograms collected on crushed single crystals, from 12 K to 295 K. The magnetic properties are similar to earlier findings demonstrating antiferromagnetic ordering below 25 K. Evidence of mag-netoelastic coupling is observed in the thermal expansion along the c-direction; not only at the low temperature antiferromagnetic transitions, but an anomalous behavior of the thermal expansion indicate magnetoelastic coupling also to the magnetic ordering related to a weak spontaneous magnetic moment appearing at 150 K. Ac-susceptibility measurements at different frequencies and superposed dc-fields are employed to further characterize this magnetic anomaly.