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- Title
Magnetocaloric effect in manganites.
- Authors
Koroleva, L.; Zashchirinskii, D.; Morozov, A.; Szymczak, R.
- Abstract
The magnetocaloric effect (MCE) in LaSrMnO, SmSrMnO, and PrBaMnO compounds is studied. The maximum values of MCE (Δ T) determined by a direct method in the second and third compositions and in LaSrMnO are found to be much lower than those calculated from the change of the magnetic part of entropy in the Curie temperature ( T) and the Néel temperature ( T) range. The negative contribution of the antiferromagnetic (AFM) part of a sample in the LaSrMnO system at 0.1 ≤ x ≤ 0.3 decreases Δ T and changes the Δ T( T) curve shape, shifting its maximum 20-40 K above T. Lower values of Δ T are detected in the range T = 130−142 K in polycrystalline and single-crystal SmSrMnO samples cooled in air. If such samples were cooled in an oxygen atmosphere (which restores broken Mn-O-Mn bonds and, thus, increases the volume of CE-type AFM clusters), the maximum in the temperature dependence of MCE is located at T (243 K) for CE-type AFM clusters. A magnetic field applied to a sample during the MCE measurements transforms these clusters into a ferromagnetic (FM) state, and both types of clusters decompose at T = T. The PrBaMnO composition undergoes an AFM-FM transition at 231 K, and the temperature dependence of its MCE has a sharp minimum at T = 234 K, where MCE is negative, and a broad maximum covering T. The absolute values of MCE at both extrema are several times lower than those calculated from the change in the magnetic entropy. These phenomena are explained by the presence of a magnetically heterogeneous FM-AFM state in these manganites.
- Subjects
MANGANITE; LANTHANUM compounds; SAMARIUM compounds; PRASEODYMIUM; ENTROPY; CURIE temperature; ANTIFERROMAGNETIC materials; SINGLE crystals
- Publication
Journal of Experimental & Theoretical Physics, 2012, Vol 115, Issue 4, p653
- ISSN
1063-7761
- Publication type
Article
- DOI
10.1134/S1063776112100044