High magnetic polarizability of magnetoresistive manganese oxides

The effects of isovalent substitution into the lanthanide sites on the magnetoresistance of La0.67-xYxCa0.33MnO3-delta oxides are presented. We will provide evidence that a key signature of the magnetic properties of these oxides is the presence of an unusual long tail in the magnetization vs temperature curves M(T), extending well above the Curie temperature and which is very sensitive to the applied magnetic field and becomes increasingly important with the concentration Of Y in the lattice. These features signal a strong polarizability of the spin clouds in these materials as our Mossbauer experiments will clearly demonstrate.