Ten Layered Hexagonal Perovskite Sr5Ru5−xO15 (x = 0.90), a Weak Ferromagnet with a Giant Coercive Field Hc 12 T

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• 作者：Ayako Yamamoto ; Daisuke Hashizume ; Hiroko Aruga Katori ; Takahiko Sasaki ; Eiji Ohmichi ; Terukazu Nishizaki ; Norio Kobayashi ; Hidenori Takagi
• 刊名：Chemistry of Materials
• 出版年：2010
• 出版时间：October 26, 2010
• 年：2010
• 卷：22
• 期：20
• 页码：5712-5717
• 全文大小：823K
• 年卷期：v.22,no.20(October 26, 2010)
• ISSN：1520-5002

文摘

A single crystal of Sr₅Ru_5−xO₁₅ (x = 0.90(2)) with mixed valence of Ru(IV) and Ru(V) was synthesized under a high pressure of 4 GPa with an oxidizer. Sr₅Ru_5−xO₁₅ crystallizes in a hexagonal perovskite-type structure with a space group P6₃/mmc (No.194), a = 5.5600(11) Å, and c = 22.830(5) Å. An alternative stacking of four corner-sharing (c) SrO₃ layers and one face-sharing (h) SrO₃ layer linking RuO₆ octahedra and its doubling along c-axis gives a 10 layer period hexagonal cell (10H) which is denoted by (cccch)₂. The partial deficiency of Ru found in face-sharing octahedra, as reported for 8H-Sr₄Ru_4−xO₁₂ (x = 0.95) with (ccch)₂ stacking, yields an average Ru valence estimate of 4.87. The bond valence analysis indicates that the valence of Ru in fully corner-sharing octahedra is nearly 5, while that of Ru in face-sharing octahedra is considerably lower than 5. This compound is a weakly ferromagnetic metal with Curie temperature T_c = 160 K and a saturated moment of 0.07 and 0.05 μ_B/Ru in H c and H // c, respectively. In the ferromagnetic state, we found remarkable enhancement of the coercivity below 50 K. At 1.7 K, a giant coercive field of 12 T was observed. We argue that Ru(IV,V) in face-sharing layers are responsible for the ferromagnetism and that possible glassy character due to frustration and disorder may at least in part contribute to the giant coercivity.