1998/06/30 by L. Vasiliu-Doloc, J. W. Lynn, A. H. Moudden +2
Earth and Planetary Sciences · Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Condensed matter physics #Dispersion relation #Ferromagnetism #High-pressure geophysics and materials #Magnetic and transport properties of perovskites and related materials #Physics #Spin wave #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.58.14913
8 pages (RevTex), 9 figures (encapsulated postscript)
arxiv created 1998/06/30 · openalex publication_date 1998/12/01 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Neutron scattering has been used to study the structure and spin dynamics of La0.85Sr0.15MnO3. The magnetic structure of this system is ferromagnetic below TC\ensuremath≃235K. We see anomalies in the Bragg peak intensities and new superlattice peaks consistent with the onset of a spin-canted phase below TCA\ensuremath∼205K, which appears to be associated with a small gap at q=(0,0,0.5) in the spin-wave spectrum. Anomalies in the lattice parameters indicate a concomitant lattice distortion. The long-wavelength magnetic excitations are found to be conventional spin waves, with a gapless (<0.02meV) isotropic dispersion relation E=Dq2. The spin stiffness constant D has a T5/2 dependence at low T, and the damping at small q follows q4T2. An anomalously strong quasielastic component, however, develops at small wave vector above \ensuremath∼200K and dominates the fluctuation spectrum as \stackrel\ensuremath→TTC. At larger q, on the other hand, the magnetic excitations become heavily damped at low temperatures, indicating that spin waves in this regime are not eigenstates of the system, while raising the temperature dramatically increases the damping. The strength of the spin-wave damping also depends strongly on the symmetry direction in the crystal. These anomalous damping effects are likely due to the itinerant character of the eg electrons.