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