The x-ray magnetic circular dichroism spin sum rule for 3d⁴ systems: Mn³⁺ ions in colossal magnetoresistance manganites

The colossal magnetoresistance manganites La^0.87±0.02Sr^0.12±0.02MnO^3+δ, La^0.78±0.02Sr^0.17±0.02MnO^3+δ, and La^0.66±0.02Sr^0.36±0.02MnO^{3+ δ} (δ close to 0) were investigated by using soft x-ray magnetic circular dichroism (XMCD) and magnetometry. Very good agreement between the values for the average Mn magnetic moments determined with these two methods was achieved by correcting the XMCD spin sum rule results by means of charge transfer multiplet calculations, which also suggest a charge transfer of ~50% for Mn⁴⁺ and ~_30% for Mn³⁺. The magnetic moment was found to be localized at the Mn ions for x = 0.17 and 0.36 at 80 K and for x = 0:12 in the temperature range from 80 to 300 K. We discuss our findings in the light of previously published data, confirming the validity of our approach.