| CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES |
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Structural, Magnetic and Magnetocaloric Properties of La-deficient La0.77-xSrxCa0.2MnO3 Perovskites |
| ZHAO Xu1, CHEN Wei1, LI Ai-Jun1,2, MA Li-Mei1, ZONG Yun1 |
| 1Department of Physics and Hebei Advanced Thin Film Laboratory, Hebei Normal University, Shijiazhuang 0500162Department of Physics, Xi'an Institute of High Technology, Xi'an 710025 |
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| Cite this article: |
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ZHAO Xu, CHEN Wei, LI Ai-Jun et al 2009 Chin. Phys. Lett. 26 087401 |
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Abstract La-deficient La0.77-xCa0.2SrxMnO3 (0≤x≤0.1) polycrystalline samples are synthesized using the sol-gel technique. The crystal structures of all the samples are single orthorhombic phase with Pbnm space group. Rietveld analysis of x-ray diffraction patterns shows that the Mn-O-Mn bond angle θMn-O-Mn increases whereas the Mn-O bond length dMn--O decreases monotonically with increasing Sr2+ content, which results in a rich overlap between Mn 3d and O 2p orbitals and leads to a systematic increase of the Curie temperature in this compound. It is found that the magnetic entropy change has a maximum at x=0.06 in La3+-deficient La0.77-xCa0.2SrxMnO3. This may result from competition between the super-exchange interactions (Mn4+-O2--Mn4+) and double-exchange interactions (Mn3+-O2--Mn4+) originating from the appearance of superfluous Mn4+ ions by substitution of Sr2+ for La3+ in this series. Large magnetic entropy changes of 2.32 and 1.83Jkg-1K-1 in the x= 0.06 and x= 0.1 samples at their TCs of 271K and 303K upon a low magnetic field (10kOe) make these materials promising candidates at near room temperature.
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| Keywords:
74.25.Ha
75.30.Sg
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Received: 11 March 2009
Published: 30 July 2009
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| PACS: |
74.25.Ha
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(Magnetic properties including vortex structures and related phenomena)
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75.30.Sg
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(Magnetocaloric effect, magnetic cooling)
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