Spin waves throughout the Brillouin zone and magnetic exchange coupling in ferromagnetic metallic manganites La$$_{1-x}$$Ca$$_{x}$$MnO$$_3$$ ($x=0.25,0.30$)
- ORNL
- ISIS Facility, Rutherford Appleton Laboratory
- Correlated Electron Research Center (CERC), Japan
- University of Tokyo, Tokyo, Japan
Using time-of-flight and triple-axis inelastic neutron spectroscopy, we determine spin wave excitations throughout the Brillouin zone for ferromagnetic manganites La$$_{1-x}$$Ca$$_x$$MnO$$_3$$ ($x=0.25,0.3$) in their low temperature metallic states. While spin wave excitations in the long wavelength limit (spin stiffness $$D$$) have similar values for both compounds, the excitations near the Brillouin zone boundary of La$$_{0.7}$$Ca$$_{0.3}$$MnO$$_3$$ are considerable softened in all symmetry directions compared to that of La$$_{0.75}$$Ca$$_{0.25}$$MnO$$_3$$. A Heisenberg model with the nearest neighbor and the fourth neighbor exchange interactions can describe the overall dispersion curves fairly well. We compare the data with various theoretical models describing the spin excitations of ferromagnetic manganites.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). High Flux Isotope Reactor (HFIR)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 936815
- Journal Information:
- Physical Review B, Vol. 75
- Country of Publication:
- United States
- Language:
- English
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