Electron, spin-wave, hyperfine, and phonon contributions to the low-temperature specific heat of La{sub 0.65}Ca{sub 0.35}MnO{sub 3}: Effects of magnetic fields and {sup 16}O/{sup 18}O exchange
The field-dependent low-temperature specific heat of an optimally doped polycrystalline sample of La{sub 0.65}Ca{sub 0.35}MnO{sub 3} (T{sub C}=265 K), 1{<=}T{le}32 K and 0{<=}H{le}9 T was analyzed by a global least-square fit to separate the hyperfine, electronic, spin-wave, and lattice contributions. The hyperfine and spin-wave contributions are in quantitative agreement with nuclear magnetic resonance and inelastic neutron-scattering results, respectively. This agreement supports the validity of both the data and their analysis. The calculated band-structure electron density of states is enhanced by a factor of 1.25. Specific heat was measured for two pieces cut from the {sup 16}O parent sample and processed in parallel to produce an {sup 18}O and a reference {sup 16}O sample. The parallel-processed samples have very much larger lattice contributions ({approx}50% at low temperatures) than the parent sample, and a somewhat larger electronic contribution. Evidently, the many processing cycles needed for {sup 18}O homogeneity produced modifications to both the long-wavelength phonons and the electron density of states. The spin-wave contribution has a small shift -- nearly within the experimental accuracy -- expected for the {sup 18}O/{sup 16}O exchange, while the hyperfine contribution is independent of isotope composition.
- Research Organization:
- Lawrence Berkeley National Laboratory
- Sponsoring Organization:
- (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 40277655
- Report Number(s):
- LBNL-49089; TRN: US0110190
- Journal Information:
- Physical Review B, Vol. 64, Issue 13; Other Information: DOI: 10.1103/PhysRevB.64.134425; Othernumber: PRBMDO000064000013134425000001; 044137PRB; PBD: 1 Oct 2001; ISSN 0163-1829
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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