SANS study of magnetic phase transitions in CaMn7O12

The mixed valence manganite CaMn7O12 system has a modulated magnetic orderi ng below 90 K which gives magnetic satellite reflections at Q < 0.2 Angstro m(-1). The results of small-angle neutron scattering (SANS) measurements on polycrystalline CaMn7O12 with and without external magnetic fields are dis cussed. It was found that near 50 K there is a second magnetic phase transi tion connected with a splitting of the satellite reflection. The Q(MAX) pos itions, intensities and half-widths of the reflections depend on temperatur e. The influence of the external magnetic held on the magnetic ordering is also discussed. (C) 2000 Elsevier Science B.V, All rights reserved.