BaFeO3: A Ferromagnetic Iron Oxide
BaFeO3: A Ferromagnetic Iron Oxide
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DOI：
10.1002/anie.201105276
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发表时间：
2011-01-01
影响因子：
16.6
通讯作者：
Takano, Mikio
中科院分区：
文献类型：
--
作者：
Hayashi, Naoaki;Yamamoto, Takafumi;Takano, Mikio
已知有一小类氧化物含有高价态Fe 4+（d4）的铁。最具代表性的相是SrFeO 3（SFO），其在立方钙钛矿结构中结晶，所述立方钙钛矿结构包含角共享（FeO 6）12 π八面体和占据所得大的开放空隙的Sr 2+离子。研究表明，SFO及其相关氧化物的行为与Fe 2+和Fe 3+氧化物如FeO、Fe 2 +/3+ 3 O 4和LaFe 3 +O3（LFO）非常不同。据我们所知，所有这些Fe 2+和Fe 3+氧化物在基态都是反铁磁（或亚铁磁）绝缘体。化合价混合通常会产生良好的导电性，但即使是最著名的Fe 3 O 4的情况下，0.11 eV的绝缘间隙[1]最终在119 K打开（Verwey跃迁）。Fe 3 O 4和Y3 Fe 3 + 5 O 12具有非平凡的自发磁化强度，每个Fe离子约为1 mB，但这些值是由于反铁磁子晶格之间的简单不平衡而不是铁磁性。相反，Fe 4+氧化物通常表现出向金属性和铁磁性的转变。SFO保持立方对称性下降到低温，尽管固有的不稳定性的双重轨道简并t2 g 3eg 1配置，并在同一时间，保持金属导电性下降到低温。[2，3] SFO表面上是一种反铁磁体（TN% 134 K），但在具有长波长的螺旋自旋结构中，最近邻自旋的角度仅约为468（4 K时每个Fe离子为3.1 mB）。[4，5]此外，当比容压缩到V（7 GPa）/V（0 GPa）= 0.95时，出现真正的铁磁性。[6]正如我们最近关于Fe 4+氧化物SrCu 2+的报告所讨论的那样，
A small class of oxides that contain iron in a high valence state of Fe4+(d4) are known. The most representative phase is SrFeO3 (SFO) that crystallizes in the cubic perovskite structure containing corner-sharing (FeO6) 12À octahedra and Sr2+ ions that occupy the resulting large open voids. It has been shown that SFO and related oxides behave very differently from Fe2+ and Fe3+ oxides such as FeO, Fe2+/3+ 3O4, and LaFe3+O3 (LFO). To the best of our knowledge, all these Fe2+ and Fe3+ oxides are antiferromagnetic (or ferrimagnetic) insulators in their ground states. Valence mixing often generates good electrical conductivity, but even for the most well-known case of Fe3O4, an insulating gap of 0.11 eV [1] eventually opens at 119K (the Verwey transition). Fe3O4 and Y3Fe3+ 5O12 have nontrivial spontaneous magnetizations of approximately 1 mB per Fe ion, but these values are due to simple imbalance between the antiferromagnetic sublattices and not to ferromagnetism. In contrast, the Fe4+ oxides commonly exhibit a shift toward metallicity and ferromagnetism. SFO maintains cubic symmetry down to low temperatures in spite of the instability inherent to the twofold orbitally degenerate t2g 3eg 1 configuration and, at the same time, maintains metallic conductivity down to low temperatures.[2, 3] SFO is seemingly an antiferromagnet (TN% 134 K), but the nearest neighboring spins make an angle of only approximately 468 (3.1 mB per Fe ion at 4 K) in the helicoidal spin structure with a long wavelength.[4, 5] Moreover, genuine ferromagnetism appears when the specific volume is compressed to V (7 GPa)/V (0 GPa)= 0.95.[6] As discussed in our recent report on an Fe4+ oxide SrCu2+