Specific heats of the pyrochlore compounds Y2Mo2O7and Y2Ru2O7

摘要

The specific heats of the pyrochlore compounds Y2Mo2O7were measured below 20 K. The Y2Ru2O7data were found to be well described by the expressionC=ggr;T+agr;T3below 7 K with a ggr; value of 2.92plusmn;0.1 mJ/mole K2and an agr; value of 0.236plusmn;0.015 mJ/mole K4. A correct description for the Y2Mo2O7data was not obvious since there was, in addition to ggr;T+agr;T3contributions, a Schottkyhyphen;like term with a maximum near 12 K plus a smaller contribution near 3.5 K of unknown origin. The ggr; and agr; values of 1.33plusmn;1 mJ/mole K2and 0.973plusmn;0.06 mJ/mole K4, respectively, should be used with caution. Neutron diffraction data were taken at 300, 77, 13, and 4.2 K on Y2Mo2O7. The results indicated that no transition to an antiferromagnetically ordered state occurred down to 4.2 K.