Electrical and magnetic properties of R 2Mo 2O 7 (R=Nd, Sm, Gd and Dy)

Abstract

We have made detailed studies of pyrochlore compounds, R 2Mo 2O 7 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 (Gd 1− x Dy x ) 2Mo 2O 7 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) 2Mo 2O 7 becomes unstable at higher pressures, and gives way to a spin glass phase that is found to exist at lower temperatures.