NEUTRON-SCATTERING INVESTIGATION OF THE STRUCTURE AND SPIN DYNAMICS IN LA0.85SR0.15MNO3

We have performed diffraction and inelastic neutron scattering experim ents on La0.85Sr0.15MnO3 single crystal. In the ferromagnetic phase of this system (T-C=235 K) the long wavelength dispersion relation along the (0,1,0) direction is well represented by E=E-0+Dq(2), but with th e spin wave spectrum almost gapless (E-0<0.1 meV), and with D-T=0=83.7 5+/-0.36 meV Angstrom(2). The spin-wave stiffness constant D(T) exhibi ts a power law behavior as a function of temperature, and appears to c ollapse as T-->T-C. An orthorhombic-rhombohedral structural phase tran sition is observed at T-s = 360 K, and exhibits a hysteretic character suggesting a first-order transformation. Anomalies in magnetization m easurements and Bragg peak intensities indicate the existence of a sec ond phase transition at T=200 K. (C) 1997 American Institute of Physic s.