Static Critical Behavior of the Spin-Freezing Transition in the Geometrically Frustrated Pyrochlore Antiferromagnet Y2Mo2O7

Some frustrated pyrochlore antiferromagnets, such as Y2Mo2O7, show a spin-freezing transition and magnetic irreversibilities below a temperature Tf similar to what is observed in randomly frustrated spin-glasses. We present results of nonlinear dc magnetization measurements on Y2Mo2O7 that provide strong evidence that there is an underlying thermodynamic phase transition at Tf, which is characterized by critical exponents γ≈2.8 and β≈0.8. These values are typical of those found in random spin-glasses, despite the fact that the level of random disorder in Y2Mo2O7 is immeasurably small.