Magnetic properties of KGd(WO4)2 studied by EPR spectroscopy.

      Аннотация: Crystal structure, magnetic and vibrational properties of KGd(WO4)2 crystals and powders in dependence on temperature were studied. EPR and Raman spectroscopy as well as crystallographic measurements were applied. Results of the Raman and crystallographic measurements do not point out any structural transition up to 4 K. The EPR spectra of KGd(WO4)2 single crystal recorded in ab, bc and ac planes in temperature range 8-300 K are broad and reveal complex shape. Two approximations were used to describe magnetic interactions inside the crystal: diluted medium and concentrated one. Detailed analysis suggests contribution of several magnetically inequivalent centers. Temperature dependences of EPR resonance lines positions, linewidths and anisotropy factor as well as angular dependences were measured and calculated taking into account superposition of three at least different lines. The dependences reveal two temperatures at which a behaviour of the total intensity suddenly changes: ~67 K and ~10 K. We assigned them to a change in a kind of dominating magnetic interactions or activity of different magnetic systems, e.g. inter-chains, intra-chains and pairs or clusters.

Ключевые слова: double tungstate, KGd(WO4)2, EPR spectra, magnetic systems