Crystal and magnetic structures of (La0.70Ca0.30)(CryMn1-y)O3: A neutron powder diffraction study

摘要: The crystal and magnetic structures of $({\mathrm{La}}_{0.70}{\mathrm{Ca}}_{0.30})({\mathrm{Cr}}_{y}{\mathrm{Mn}}_{1\ensuremath{-}y}){\mathrm{O}}_{3}$ for $y=0.70$, 0.50, 0.15 have been investigated using neutron powder diffraction. three samples crystallize in the $Pnma$ space group at both 290 $5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ exhibit different low temperature. In $({\mathrm{La}}_{0.70}{\mathrm{Ca}}_{0.30})({\mathrm{Cr}}_{0.70}{\mathrm{Mn}}_{0.30}){\mathrm{O}}_{3}$, antiferromagnetic order with a propagation vector $\mathbit{k}=0$ sets in. structure is ${G}_{x}$, i.e., $G$ type spins parallel to $a$ axis. On basis our Rietveld refinement available magnetization data, we speculate that only ${\mathrm{Cr}}^{3+}$ order, whereas ${\mathrm{Mn}}^{4+}$ act as random impurities. $({\mathrm{La}}_{0.70}{\mathrm{Ca}}_{0.30})({\mathrm{Cr}}_{0.50}{\mathrm{Mn}}_{0.50}){\mathrm{O}}_{3}$ spin still although net moment smaller. No evidence Mn ions observed. Finally, $({\mathrm{La}}_{0.70}{\mathrm{Ca}}_{0.30})({\mathrm{Cr}}_{0.15}{\mathrm{Mn}}_{0.85}){\mathrm{O}}_{3}$ ferromagnetic ordering takes place, impurities randomly oriented spins.