Static Critical Behavior of the Spin-Freezing Transition in the Geometrically Frustrated Pyrochlore Antiferromagnet Y 2 Mo 2 O 7

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 $\ensuremath{\gamma}\ensuremath{\approx}2.8$ and $\ensuremath{\beta}\ensuremath{\approx}0.8$. 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.