Electrical and magnetic properties of R2Mo2O7 (R=Nd, Sm, Gd and Dy)

We have made detailed studies of pyrochlore compounds, R2Mo2O7 with R=Nd, Sm, Gd, and Dy. For R=Nd and Sm, we found that apart from the ferromagnetic transition of Mo moments there is another transition of a reentrant spin glass type at lower temperatures, where both the magnetization and heat capacity data show anomalous features. We also observed that the AC susceptibility data are clearly frequency-dependent even in the ferromagnetic phase. In our pressure-dependent magnetization studies, the magnetization data of (Gd1-xDyx)2Mo2O7 for x=0, 0.1, 0.2, and 0.4 are found to decrease continuously with pressures and, simultaneously, the ferromagnetic transition temperatures move towards lower temperatures. Eventually the ferromagnetic state of (Gd,Dy)2Mo2O7 becomes unstable at higher pressures, and gives way to a spin glass phase that is found to exist at lower temperatures