Element-specific and bulk magnetism, electronic, and crystal structures of La0.70Ca0.30Mn1-xCrxO3

The magnetic interactions in La_0.70Ca_0.30Mn_1-xCr_xO₃ (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 Cr³⁺ 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 T_N=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 T_c=224 K. For x=0.50, a reduced ferrimagnetic component dominated by Mn spins is present below T_c=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.