Investigation of the magnetic properties of Y2Ru2O7 by 99Ru Mossbauer spectroscopy

Magnetic properties of the Mott insulator with the pyrochlore structure Y2Ru2O7 were investigated using Ru-99 Mossbauer spectroscopy. Bulk magnetization measurements confirmed appearance of the spin-glass-like antiferromagnetic order with very large differences between zero-field-cooled and field-cooled magnetizations below the Neel temperature T-N=76(2) K. The Mossbauer spectra were obtained above and below T-N. Analysis of the spectrum recorded at 4.2 K suggested a noncollinear local ordering of ruthenium magnetic moments. The electronic structure of the individual ruthenium ion, responsible for magnitudes of hyperfine parameters and the ruthenium magnetic moment, was discussed within the framework of the crystalline electric-field model, including the spin-orbit coupling and the exchange interaction in the molecular-field approximation. Reasonably good agreement between calculated and experimentally determined parameters was obtained. Simultaneously, the experimentally observed easy plane of ruthenium magnetic moments was explained.