Synthesis, structure, and magnetic characterization of La2−xRxRuO5(R=Pr, Nd, Sm, Gd, Dy)

Abstract

Polycrystalline samples of La${}_{2\ensuremath{-}x}{R}_{x}$RuO${}_{5}$ ($R$ $=$ Pr, Nd, Sm, Gd, Dy) have been prepared, applying a soft-chemistry route based on the thermal decomposition of citric acid precursors. By powder x-ray and neutron diffraction the crystal structures have been investigated in detail. For the unsubstituted parent compound La${}_{2}$RuO${}_{5}$, synchrotron x-ray diffraction patterns reveal a broad structural phase transition regime around 170 K without any significant hysteresis. This structural transition is linked with a drastic reduction of the magnetic susceptibility. A similar behavior was also observed for the lanthanide-substituted compounds La${}_{2\ensuremath{-}x}{R}_{x}$RuO${}_{5}$. Magnetic measurements reveal the coexistence of two weakly interacting magnetic sublattices. The effect of rare-earth substitution on the magnetic phase transition is resulting from structural modifications caused by the smaller radius of the ${R}^{3+}$ ions. These ions are predominantly located within the LaO-layers, which are alternating with LaRuO${}_{4}$ layers. The transition temperatures determined by differential scanning calorimetry (DSC) are compared to data derived from the susceptibility measurements.