Structural, magnetic, and thermal properties of Ce1−xEuxCrO3 orthochromite solid solutions

Abstract

The interplay of slight changes of the rare-earth composition and antiferromagnetic ordering of Cr in a series of high purity solid solutions of orthochromites with composition ${\mathrm{Ce}}_{1\ensuremath{-}x}\mathrm{Eu}{}_{x}{\mathrm{CrO}}_{3}\phantom{\rule{4pt}{0ex}}(1\ensuremath{\leqq}x\ensuremath{\leqq}0)$ was investigated by neutron and x-ray powder diffraction, magnetization, and heat capacity measurements. A careful study of the crystal structure by x-ray powder diffraction data across the whole range of $x$ enables us to correlate the magnetic properties of the Cr magnetic subsystem with the size of the lattice and minute changes of the bond and torsion angles within and between the ${\mathrm{CrO}}_{6}$ octahedra. We find that the sizes and the shapes of the ${\mathrm{CrO}}_{6}$ octahedra remain essentially unchanged as the size of the rare-earth cations and the cell volumes are gradually reduced by Eu substitution, whereas decreasing Cr-O-Cr bond angles and increasing inclination of neighboring octahedra compensate for the decreasing lattice size. Adverse to external hydrostatic pressure that reduces the cell volume but raises the ordering temperature, lowering the cell volume by replacing Ce by Eu decreases the N\'eel temperature linearly with the Eu concentration from 260 K for ${\mathrm{CeCrO}}_{3}$ to 178 K for ${\mathrm{EuCrO}}_{3}$.