Glassy correlated state induced by disorder in the frustrated antiferromagnet Tb2Zr2O7

We study the low-temperature thermomagnetic properties of the polycrystalline material Tb2Zr2O7 through ac susceptibility and specific heat measurements. This zirconate displays a defect-fluorite structure in which the magnetic Tb3+ and nonmagnetic Zr4+ cations sit randomly on the same metal sublattice. No long-range magnetic order is found down to 100 mK, although dominant antiferromagnetic interactions are observed and the spins remain dynamic down to the lowest temperatures investigated. We observed a frequency-dependent peak around 2.5 K which is well described by many models of a canonical spin-glass transition. In-field specific heat measurements and the recovered entropy of the system Rln(4) suggest a two doublets ground state separated by 7 K. Comparisons to the pyrochlores Tb2Ti2O7 and Tb2Hf2O7 reinforce the collective spin-glass-type behavior and the opening for discussions of an exotic Coulomb phase in this material.