Isovalent-substitution effect on the Verwey-type transition in the A-site-ordered double perovskite (Ba,Sr)RFe2O5

J. Nakamura; M. Karppinen; P. Karen; J. Lindén; H. Yamauchi

doi:10.1103/PhysRevB.70.144104

Isovalent-substitution effect on the Verwey-type transition in the A-site-ordered double perovskite (Ba,Sr)RFe₂O₅

J. Nakamura
, M. Karppinen^*
, P. Karen
, J. Lindén
, H. Yamauchi

^*Corresponding author for this work

Research output: Contribution to journal › Article › Scientific › peer-review

5 Citations (Scopus)

Abstract

Two types of chemical-pressure effects on the Verwey-type transition in BaSmFe₂O₅ are studied, viz., ionic-size contractions at the Ba and Sm sites. Whereas the replacement of Sm by the smaller Eu and Gd atoms increases the transition temperature T_V from 232 K to 264 K, the Sr-for-Ba substitution decreases it from 232 K to 180 K for x=0.15 in (Ba_1-xSr_x)SmFe₂O₅. Of various structural parameters determined by synchrotron x-ray diffraction above T _V, the magnitude of the orthorhombic distortion (=b-a) is found to correlate with T_V in a manner that unifies both substitution schemes. It is suggested that when an increase in b-a above T_V is achieved by means of the structural substitution, it makes it easier for the d_xz Fe²⁺ orbital ordering to occur below T_V.

Original language	English
Article number	144104
Pages (from-to)	144104-1-144104-6
Journal	Physical Review B - Condensed Matter and Materials Physics
Volume	70
Issue number	14
DOIs	https://doi.org/10.1103/PhysRevB.70.144104
Publication status	Published - Oct 2004
MoE publication type	A1 Journal article-refereed

Funding

This work was supported by Grants-in-aid for Scientific Research (Nos. 15206002 and 15206071) from the Japan Society for the Promotion of Science. The synchrotron radiation experiments were performed under the auspices of SPring-8 (PRC No. 2002B0170). Professor Satoshi Sasaki and Dr. Ken-ichi Kato and Dr. Kouji Yamawaki are thanked for their experimental guidance.

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10.1103/PhysRevB.70.144104

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title = "Isovalent-substitution effect on the Verwey-type transition in the A-site-ordered double perovskite (Ba,Sr)RFe2O5",

abstract = "Two types of chemical-pressure effects on the Verwey-type transition in BaSmFe2O5 are studied, viz., ionic-size contractions at the Ba and Sm sites. Whereas the replacement of Sm by the smaller Eu and Gd atoms increases the transition temperature TV from 232 K to 264 K, the Sr-for-Ba substitution decreases it from 232 K to 180 K for x=0.15 in (Ba1-xSrx)SmFe2O5. Of various structural parameters determined by synchrotron x-ray diffraction above T V, the magnitude of the orthorhombic distortion (=b-a) is found to correlate with TV in a manner that unifies both substitution schemes. It is suggested that when an increase in b-a above TV is achieved by means of the structural substitution, it makes it easier for the dxz Fe2+ orbital ordering to occur below TV.",

author = "J. Nakamura and M. Karppinen and P. Karen and J. Lind{\'e}n and H. Yamauchi",

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AU - Lindén, J.

AU - Yamauchi, H.

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AB - Two types of chemical-pressure effects on the Verwey-type transition in BaSmFe2O5 are studied, viz., ionic-size contractions at the Ba and Sm sites. Whereas the replacement of Sm by the smaller Eu and Gd atoms increases the transition temperature TV from 232 K to 264 K, the Sr-for-Ba substitution decreases it from 232 K to 180 K for x=0.15 in (Ba1-xSrx)SmFe2O5. Of various structural parameters determined by synchrotron x-ray diffraction above T V, the magnitude of the orthorhombic distortion (=b-a) is found to correlate with TV in a manner that unifies both substitution schemes. It is suggested that when an increase in b-a above TV is achieved by means of the structural substitution, it makes it easier for the dxz Fe2+ orbital ordering to occur below TV.

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Isovalent-substitution effect on the Verwey-type transition in the A-site-ordered double perovskite (Ba,Sr)RFe₂O₅

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