Static Critical Behavior of the Spin-Freezing Transition in the Geometrically Frustrated Pyrochlore AntiferromagnetY2Mo2O7

Abstract

Some frustrated pyrochlore antiferromagnets, such as ${\mathrm{Y}}_2$M${\mathrm{o}}_2$ ${\mathrm{O}}_7$, show a spin-freezing transition and magnetic irreversibilities below a temperature $T_f$ similar to what is observed in randomly frustrated spin-glasses. We present results of nonlinear dc magnetization measurements on ${\mathrm{Y}}_2$M${\mathrm{o}}_2$ ${\mathrm{O}}_7$ that provide strong evidence that there is an underlying thermodynamic phase transition at $T_f$, which is characterized by critical exponents $\gamma \approx 2.8$ and $\beta \approx 0.8$. These values are typical of those found in random spin-glasses, despite the fact that the level of random disorder in ${\mathrm{Y}}_2$M${\mathrm{o}}_2$ ${\mathrm{O}}_7$ is immeasurably small.