Crystal structure, magnetic properties, x-ray-photoemission-spectroscopy, and specific-heat measurements on ${\mathrm{Pr}}_2$${\mathrm{BaO}}_4$ and ${\mathrm{PrBaO}}_3$

We investigated ${\mathrm{Pr}}_2$${\mathrm{BaO}}_4$ and ${\mathrm{PrBaO}}_3$ by several complementary experimental techniques. ${\mathrm{PrBaO}}_3$ crystallize in an orthorhombic structure. dc and ac susceptibility measurements exhibit irreversibility phenomena below ${\mathit{T}}_{\mathit{N}}$=11.7 K and reveal the magnetic structure of ${\mathrm{PrBaO}}_3$, which consists of an antiferromagnetic ordering together with a small canting of the spins which produces the ferromagnetic component. Both magnetic and specific-heat studies show that ${\mathit{T}}_{\mathit{N}}$ is not affected by the applied magnetic field up to 9 T. ${\mathrm{Pr}}_2$${\mathrm{BaO}}_4$ crystallizes in an orthorhombic structure where a=10.56 Å, b=12.43 Å, and c=3.617 Å belongs to Pnam space group. dc and ac susceptibility and specific-heat measurements show that ${\mathrm{Pr}}_2$${\mathrm{BaO}}_4$ is paramagnetic down to 2 K, with a vanishing electronic specific-heat coefficient γ. X-ray photoemission spectroscopy shows that Pr is mainly trivalent in ${\mathrm{Pr}}_2$${\mathrm{BaO}}_4$ and close to being tetravalent in ${\mathrm{PrBaO}}_3$. The pronounced ferromagnetic-like behavior found below 11.7 K in the ${\mathrm{Pr}}_{\mathit{x}}$${\mathit{R}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Ba}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{\mathit{z}}$ system is due to the impurity of ${\mathrm{PrBaO}}_3$.