High-pressure synthesis and sequential ferrimagnetic ordering and spin glass transition of an Fe/Ru disordered quadruple perovskite CeCu₃Fe₂Ru₂O₁₂

We successfully prepared an A-site-ordered quadruple perovskite oxide CeCu₃Fe₂Ru₂O₁₂ by using a high-pressure method (10 GPa, 1400 K). The compound crystallizes in the $Im\overline{3}$ space group, with A-site ordering of Ce and Cu ions in a ratio of 1:3, but B-site disordered distribution of Fe and Ru ions. Bond-value-sum calculations and x-ray photoelectron spectroscopy measurement manifest that the charge distribution is ${\mathrm{Ce}}^{3.5+}{\mathrm{Cu}}_3^{2+}{\mathrm{Fe}}_2^{3+}{\mathrm{Ru}}_2^{4.25+}{\mathrm{O}}_{12}$. A ferrimagnetic phase transition occurs at T_C = 73.6 K followed by a spin glass behavior at 50.3 K consistent with the conventional dynamical scaling power law. Electrical transport measurement shows that the intrinsic electrical behavior is semiconducting and the resistivity obey the adiabatic small-polaron model. The specific heat follows a T² law instead of traditional phonon-dominated T³ behavior implying a finite energy gap in the excitation spectrum.