Magnetic Coupling in the Insulating and Metallic Ferromagnetic La1-xCaxMnO3
- ORNL
Low-energy spin excitations play an essential role in determining the characteristics of the phase transitions in the colossal magnetoresistant manganese-oxides (manganites). Inelastic neutron scattering has been utilized to study the spin excitations of the ferromagnetic (FM) La{sub 1-x}Ca{sub x}MnO{sub 3} (LCMO) as a function of hole doping x (0.2, 0.25, and 0.30) and temperature, above and below the Curie temperature T{sub c}. While the spin-diffusion coefficients {Lambda}(T) and T{sub c}'s increase smoothly with doping concentration x, the spin-stiffness constant D(T) for the insulating LCMO is 3 times smaller than that of the metallic LCMO. Furthermore, the paramagnetic-to-ferromagnetic phase transitions in LCMO manganites investigated have nonvanishing extrapolated values of D(T) as T {yields} T{sub c} and nondiverging spin-correlation lengths at T{sub c}. These results present a serious challenge to the understanding of these materials using models such as Heisenberg ferromagnetism, double exchange, or modified double exchange.
- Research Organization:
- ORNL Oak Ridge National Laboratory
- Sponsoring Organization:
- DOE
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 829285
- Report Number(s):
- P01-109960
- Journal Information:
- Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 22 Vol. 64; ISSN PRBMDO; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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