Metal-Insulator Transitions in Pyrochlore Oxides Ln sub( 2)Ir sub( 2)O sub( 7)

We report the physical properties of Ln ... Ir ... O ... ( Ln = Nd, Sm, Eu, Gd, Tb, Dy, and Ho), which exhibit metal-insulator transitions (MITs) at different temperatures. The transition temperature T MI increases with a reduction in the ionic radius of Ln . The ionic radius boundary for MITs in Ln...

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Veröffentlicht in:Journal of the Physical Society of Japan 2011-09, Vol.80 (9), p.1-1
Hauptverfasser: Matsuhira, Kazuyuki, Wakeshima, Makoto, Hinatsu, Yukio, Takagi, Seishi
Format: Artikel
Sprache:eng
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Zusammenfassung:We report the physical properties of Ln ... Ir ... O ... ( Ln = Nd, Sm, Eu, Gd, Tb, Dy, and Ho), which exhibit metal-insulator transitions (MITs) at different temperatures. The transition temperature T MI increases with a reduction in the ionic radius of Ln . The ionic radius boundary for MITs in Ln ... Ir ... O ... lies between Ln = Pr and Nd. MITs in Ln ... Ir ... O ... have some common features. They are second-order transitions. Under the field cool condition, a weak ferromagnetic component (~10 -3 ... ... /f.u.) caused by Ir 5 d electrons is observed below T ... . The entropy associated with MITs for Ln = Nd, Sm, and Eu is estimated to be 0.47, 2.0, and 1.4 J/(K-mole), respectively. The change in entropy is much smaller than 2 R ln 2 [11.5 J/(K-mole)] expected in a magnetic transition due to localized moments of S = 1/2. The feature of continuous MITs in Ln ... Ir ... O ... is discussed. (ProQuest: ... denotes formulae/symbols omitted.)
ISSN:0031-9015
1347-4073