X-MCD study of mixed valence manganites

A study of the X-MCD spectra and X-MCD magnetometry, i.e. the X-MCD effect vs. applied field, of the colossal magnetoresistive perovskites La0.67-yTby Ca0.33MnO3 is reported. The spectra were measured on polycrystalline sample s with y = 0.0, 0.1, 0.22 at 10 and 77 K at the K, L-2, L-3 edges of mangan ese, the L-2, L-3 edges of lanthanum and the L-2, L-3, M-4, M-5, edges of t erbium. From the X-MCD signal at the M-4, M-5 edges of terbium a parallel a lignment of terbium sublattice magnetisation to the manganese magnetisation and to the applied magnetic field is deduced. The X-MCD magnetometry curve s at the Mn K edge and La L edges show a saturation in the applied field, w hereas Tb L edge signals do not saturate. The effect is especially pronounc ed in La0.45Tb0.22Ca0.33MnO3. The results are discussed in terms of the inf luence of terbium doping on the magnetic and electronic phase separation an d on the strength of the coupling between magnetic moments of Th and Mn and their relation to the colossal magnetoresistance of the compounds. (C) 200 1 Elsevier Science BY. All rights reserved.