SANS study of magnetic phase transitions in CaMn7O12

Complete text of publication follows. Below 80 K the mixed valence manganite CaMn7O12 system has a modulated magnetic ordering which gives magnetic satellite reflections at Q < 0.2 A-1 [1]. The results of small angle neutron scattering (SANS) measurements on polycrystalline CaMn7O12 performed with the SANS instrument V4 and the diffractometers E2 and V1 at the Berlin Neutron Scattering Center are discussed. The measurements have been performed at RT and low temperatures down to 10 K. In the range from 80 K to 49 K there is one single magnetic satellite reflection near Q = 0.115 A-1 while below 48 K two magnetic satellite peaks are observed and their Q values vary with temperature. In the vicinity of the transition temperature, i.e. near 49 K, the coherence length of the modulated magnetic ordering is considerably smaller (the satellite peaks are broadened) than both below and above 49 K. SANS measurements in a vertical do magnetic field of 4 T have been also performed. It was found that the intensity, Q position and FWHM of magnetic satellite reflections change with the external field. (author) [1] R. Przenioslo, I. Sosnowska, M. Zoltek, D. Hohlwein, I.O. Troyanchuk, Physica B 241-43, 730 (1998)