Magnetic interactions in (Pr, La)₃RuO₇ and Pr₃(Ru, Nb)O₇

Abstract

The rare-earth ruthenate Pr₃RuO₇ is a Mott insulator displaying magnetic ordering at two temperatures T _N1 = 36 K and T _N2 = 55 K. By substituting diamagnetic La for Pr and diamagnetic Nb for Ru, T _N1 is shown to be associated with ordering among the rare earths and T _N2 among the Ru cations. These results are similar to those of Sm₃RuO₇, but the ordering temperatures for Pr₃RuC₇ are large compared with all other known Ln₃MO₇ systems and there is less divergence between field-cooled and zero-field-cooled magnetic susceptibility for T < T _N2. Isothermal magnetization measurements, including pulsed-field measurements, show hysteretic-field-induced transitions at B ≈ 4T for T ≪ TN1 associated with a spin reorientation of the Pr moments. Further characterization of Pr₃RuO₇ is provided from measurements of the heat capacity for 2K < T < 17 K and electrical resistivity for 100K < T < 300 K.