  The magnetic interactions in La{0.70}Ca{0.30}Mn{1-x}Cr{x}O{3} (x = 0.15, 0.50
and 0.70) are investigated by x-ray absorption spectroscopy (XAS), x-ray
magnetic circular dichroism (XMCD), high-resolution x-ray powder diffraction,
and bulk magnetization measurements. XAS in the Mn and Cr L{2,3} edges support
stable single valent Cr{3+} ions and a varying Mn valence state with x, while
the O K edge XAS spectrum reveals local maxima in the O 2p density of states
close to the Fermi level due to mixing with Mn and Cr 3d states. A robust
antiferromagnetic state is found for x=0.70 below TN = 258 K. For x=0.15,
combined XMCD and bulk magnetization measurements indicate a fully polarized
ferrimagnetic state for the Mn and Cr spins below Tc=224 K. For x=0.50, a
reduced ferrimagnetic component dominated by Mn spins is present below Tc=154
K. No evidence of lattice anomalies due to cooperative charge and orbital
orderings is found by x-ray diffraction for all samples. The magnetic
properties of this system are rationalized in terms of a competition of
ferromagnetic Mn-Mn double exchange and antiferromagnetic Cr-Cr and Cr-Mn
superexchange interactions.
