Inorganic Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QR, United Kingdom.
Inorg Chem. 2010 Jul 5;49(13):5912-22. doi: 10.1021/ic100377s.
Polycrystalline samples of Ln(18)Li(8)Rh(5-x)Fe(x)O(39) (Ln = La, Nd; 0.5 < or = x < or = 5) have been synthesized by a solid-state method and studied by a combination of dc and ac magnetometry, neutron diffraction, and Mossbauer spectroscopy. All compositions adopt a cubic structure (space group Pm3n, a(0) approximately 12 A) based on intersecting 111 chains made up of alternating octahedral and trigonal-prismatic coordination sites. These chains occupy channels within a Ln-O framework. At low values of x, iron preferentially occupies the smaller (2a) of the two distinct octahedral sites as low-spin Fe(IV). The Rh(III) on the larger (8e) octahedral site is replaced by high-spin Fe(III). Nd-containing compositions having x > 1 show spin-glass-like behavior below approximately 5 K. La-containing compositions having x > 1 show evidence of a magnetic transition at approximately 8 K, but the nature of the transition is unclear. This contrasting behavior demonstrates that, although the structural chemistry of the two systems is essentially the same, the magnetic character of the Ln cations plays an important role in determining the properties of these compounds.
Ln(18)Li(8)Rh(5-x)Fe(x)O(39)（Ln = La、Nd；0.5 <= x <= 5）的多晶样品已通过固态法合成，并通过直流和交流磁强计、中子衍射和穆斯堡尔光谱学进行了研究。所有组成均采用立方结构（空间群 Pm3n，a(0)约为 12 A），基于交替的八面体和三角棱柱配位位形成的 111 链相交而成。这些链占据了 Ln-O 骨架内的通道。在 x 值较低的情况下，铁优先占据两个不同的八面体位中的较小位（2a），形成低自旋 Fe(IV)。较大的八面体位（8e）上的 Rh(III)被高自旋 Fe(III)取代。x > 1 的含 Nd 组成物在约 5 K 以下表现出类似自旋玻璃的行为。x > 1 的含 La 组成物在约 8 K 时表现出磁转变的证据，但转变的性质尚不清楚。这种对比行为表明，尽管两个系统的结构化学基本相同，但 Ln 阳离子的磁性在决定这些化合物的性质方面起着重要作用。
