Peculiar magnetic properties of (Dy,Ca)MnO3

The magnetic properties of the Dy1−xCaxMnO3 solid solution (0≤x≤0.60) have been studied as a function of temperature and magnetic field. A paramagnetic state, with the Curie–Weiss temperature Θ changing from −25 to +14 K, is observed from x=0 to x=0.3. At higher calcium concentration, charge ordering effects seem to dominate. Dy–Dy interactions present in the pure DyMnO3 manganite (TN=9.5 K) persist in the solid solution up to x=0.3. The Mn sublattice orders ferromagnetically at Tc∼80 K. C/FC magnetization cycles show a ferrimagnetic-like system, in which negatively-polarized dysprosium moments behave as free spins (T>TN) under the internal field of the ordered Mn sublattice. The local field at a given Dy site depends on the exchange (negative) interaction between both sublattices, resulting in a reversal of the magnetization when the magnetic moment of the Dy sublattice exceeds the one of the ferromagnetic network.