Mesoscopic magnetic inhomogeneities in the low-temperature phase and structure of Sm1-xSrxMnO3 (x < 0.5) perovskite

Results are presented of studies of the (Sm1- xSrxMnO3)-Sm-154 system using neutron powder diffraction and small-angle polarized neutron scattering. A n analysis of the neutron diffraction spectra showed that at T < 180 K thes e exhibit typical Jahn-Teller distortions of the manganese-oxygen octahedro ns which persist under further cooling and on transition of the sample to a metallic magnetically ordered state. The magnetic contribution to the diff raction is satisfactorily described using the (A(x)(A(y))F-z) model and is interpreted as the coexistence of ferromagnetic and antiferromagnetic phase s. The exaggerated widths of the diffraction lines indicate an appreciable contribution from microdeformations evidently associated with the inhomogen eity of the system. Small-angle polarized neutron scattering showed that th e Sm system for x = 0.4 and 0.25 is magnetically inhomogeneous in the low-t emperature phase. Ferromagnetic correlations occur on scales of around 200 Angstrom and having dimensions greater than 1000 Angstrom which, combined w ith the temperature hysteresis of the magnetic small-angle scattering inten sity observed for an x = 0.4 sample in the low-temperature phase, suggests that the transition is of a percolation nature. (C) 2000 MAIK "Nauka/Interp eriodica".