Thermal and Magnetic Properties of the Spin-Chain Material, Pr3RuO7

We present measurements of the magnetic moment and specific heat of single crystals of the spin-chain insulator, Pr3RuO7. The susceptibility indicates that three-dimensional antiferromagnetic order sets in at TN = 54 K, with spin polarization approximately along the chain direction, but the susceptibility anisotropy above TN indicates that the intrachain interactions are predominantly ferromagnetic while the interchain interactions are antiferromagnetic. This competition presumably gives rise to the observed metamagnetic behavior for applied fields along the polarization direction. The specific heat anomaly at TN is unusually mean-field in shape, with magnitude indicating that the transition involves mostly ordering of the ruthenium moments. A Schottky-like anomaly at low temperature may be due to praesodynium ions ordering in the effective field established at TN.