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
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
摘要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.
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.
[1] Liu G J et al 2007 Appl. Phys. Lett. 90032507 [2] Zhang X Y et al 2008 J Appl. Phys. 103 07B303 [3] Zemni S et al 2009 Mater. Lett. 63 489 [4] Guo ZB et al 1997 Phys. Rev. Lett. 78 1142 [5] Gschneidner KA Jr et al 2005 Rep. Prog. Phys. 68 1479 [6] Phan M H et al 2004 J. Appl. Phys 96 1154 [7] Dinesen AR et al 2005 Phys: Condens. Matter 17 6257 [8] Lin G C et al 2005 Mater. Lett. 59 2149 [9] Chen W et al 2002 J. Phys: Condens. Matter 1411889 [10] Phan M H et al 2003 J. Magn. Magn. Mater. 262 407 [11] Lin G C et al 2004 J. Magn. Magn. Mater. 283375 [12] Rietveld H M 1969 J. Appl. Crystallogr. 2 65 [13] Phan M H et al 2005 Appl. Phys. Lett. 86072504 [14] Mira J et al 2002 J. Appl. Phys. 91 8903 [15] Radaelli PG et al 1997 Phys. Rev. B 56 8265 [16] Wang Z M et al 2001 J. Appl. Phys. 90 5689
2009, Vol. 26 
