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

The crystal and magnetic structures of ͑La0.70Ca0.30͒͑CryMn1−y͒O3 for y = 0.70, 0.50, and 0.15 have been investigated using neutron powder diffraction. The three samples crystallize in the Pnma space group at both 290 and 5 K and exhibit different magnetic structures at low temperature. In ͑La0.70Ca0.30͒͑Cr0.70Mn0.30͒O 3, antiferromagnetic order with a propagation vector k = 0 sets in. The magnetic structure is Gx, i.e., of G type with spins parallel to the a axis. On the basis of our Rietveld refinement and the available magnetization data, we speculate that only Cr 3+ spins order, whereas Mn4+ act as random magnetic impurities. In ͑La0.70Ca0.30͒͑Cr0.50Mn0.50͒O 3 the spin order is still of the type Gx, although the net magnetic moment is smaller. No evidence for magnetic order of the Mn ions is observed. Finally, in ͑La0.70Ca0.30͒͑Cr0.15Mn0.85͒O3 a ferromagnetic ordering of the Mn spins takes place, whereas the Cr3+ ions act as random magnetic impurities with randomly oriented spins.