Anomalous Specific Heat of Multiferroic BiFeO 3

The specific heat of BiFeO 3 (BFO) is studied using a Green’s function. A microscopic quantum model is employed to describe the BFO. Note that this mechanism also includes the anharmonic phonon–phonon interaction. It is shown that the specific heat of BFO exhibits a peak at Neel temperature ( T N )....

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Bibliographic Details
Published in:Journal of low temperature physics 2017-11, Vol.189 (3), p.196-203
Main Author: Xian-Sheng Cao
Format: Article
Language:English
Subjects:
Anharmonicity
Curie temperature
Ferroelectric materials
Ferroelectricity
Heat
Low temperature physics
Multiferroic materials
Neel temperature
Specific heat
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Summary:The specific heat of BiFeO 3 (BFO) is studied using a Green’s function. A microscopic quantum model is employed to describe the BFO. Note that this mechanism also includes the anharmonic phonon–phonon interaction. It is shown that the specific heat of BFO exhibits a peak at Neel temperature ( T N ). This result can be explained as an effect of vanishing magnetic ordering above T N . In addition, magnetic subsystem has no effect on the ferroelectric above T N for T N ≪ T C (Curie temperature). It is found that the peak of the specific heat positions shifts to higher temperature with the parameters of the anharmonic phonon ( V ( 3 ) and V ( 4 ) ) and the second-order pseudo-spin–phonon interaction ( | R E | ) increases, whereas the peak of specific heat positions shifts to lower temperature when the second-order spin–phonon interaction ( | R M | ) increases. Those theoretical results are in agreement with the results of the experiment.
ISSN:0022-2291
1573-7357
DOI:10.1007/s10909-017-1804-0