A comparison of the local magnetic susceptibility in rare earth pyrochlores

We report transverse field muon spin rotation studies of the rare earth pyrochlores Gd2Ti2O7 and Tb2Ti2O7. The paramagnetic shift in the observed precession frequency depends on the local spin susceptibility and probes the contact hyperfine and dipolar fields at the muon site within these materials. The results are compared with measurements of the bulk susceptibility. While no features associated with magnetic ordering are observed down to 0.015K, hysteretic behavior develops in Tb2Ti2O7 below T=1K, likely due to the formation of clusters of ferromagnetically correlated spins.