Diamagnetic to paramagnetic transition in LaCoO{sub 3}.
The diamagnetic to paramagnetic spin state transition in LaCoO{sub 3} (LCO) that occurs in the temperature range 30-120 K is generally attributed to the small energy gap between the Co{sup 3+} t{sub 2g} and e{sub g} states. Evidence for this thermally activated transition has been interpreted as leading to either the intermediate spin state, t{sub 2g} {sup 5}e{sub g} {sup 1}(S=1), or, alternatively, to the high-spin state, t{sub 2g} {sup 4}e{sub g} {sup 2}(S=2) of the Co{sup 3+} ion, with the issue proving highly controversial. In an effort to obtain a consistent description of the temperature dependence of the magnetic and thermal properties of this system, we have made measurements of both the magnetization in applied fields of up to 33 T and the specific heat at 0 and 9 T on a single crystal of LCO. In addition, EPR measurements were made on the same sample using high-field EPR spectrometers. The spin-Hamiltonian parameters are consistent with the previous pulsed-field EPR work and support the atomic-like energy level description of the Co ion. The low-lying first-excited state is part of the {sup 5}T{sub 2g} ({sup 5}D) set and is a triplet state with effective spin S{sub eff}=1. The magnetization results are analyzed using a mean-field model allowing for antiferromagnetic correlations between the spins. The model is used to estimate the spin contribution to the specific heat.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); State of Florida
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 958030
- Report Number(s):
- ANL/MSD/JA-63268; TRN: US201002%%216
- Journal Information:
- Phys. Rev. B, Vol. 79, Issue 2009; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- ENGLISH
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