Small angle neutron scattering study of magnetic clustering in (Pr0.55Ca0.45)(Mn1-yCry)O3 manganites

In the present paper we report a small angle neutron scattering (SANS) study of magnetic clusters formation in (Pr0.55Ca0.45)(Mn1yCry)O3 (y = 0.00, 0.03, 0.06) manganites which was performed by analyzing, above and below the magnetic phase transitions, the momentum transfer q dependence of the SANS intensity on temperature and on the applied magnetic field 0 < H < 5 T. Thermal scans between 5 and 300 K in zero field, 1 and 5 T as well as isothermal field-scans at three different temperatures were collected in the suitable q range on each sample. These measurements allowed us to determine the spatial dimensions, density and distribution of the non-overlapping ferromagnetic clusters before, during and after their formation, both in the insulating high temperature and in the percolating low temperature phases. Our results indicate that the magnetic clusters formation is favoured by Mn/Cr partial substitution, thus emphasizing the importance of magnetic polarons in the natural tendency of manganites to phase separation and the possibility to tune by chemical substitution the relative weight of one phase component with respect to the other one.