Crystal Chemistry and Magnetic Properties of Layered Metal Oxides Possessing the K₂NiF₄ or Related Structures

Abstract

There is increasing interest in recent years in the structural chemistry and properties of layered metal oxides possessing the K2NiF4 or related structures. Many new oxides of this structure exhibiting novel properties are being reported from time to time in the literature. The crystal chemistry of the oxides of the general formula A2B04 with particular reference to the stability of the K2NiF4 structure and the relations between the different structures exhibited by this family of oxides is discussed. Non-stoichiometry in these oxides is another aspect of interest discussed in the article. While K2NiF4 itself is a well-known two-dimensional antiferromagnet, oxides of this structure with a variety of magnetic properties are examined in some detail. Besides the ternary A2BO4 oxides, the structure and magnetic properties of complex oxides, where the A or/and the B ions are partly substituted by other cations, is discussed. Some of the problems related to this family of oxides that are worth investigating are indicated. Much of the discussion in this article would have relevance in understanding the structure and properties of layered materials.

Structure and Microwave Dielectric Properties of Solid Solution in SrLaAlO4‐Sr2TiO4 System

“…The abnormally reduced Qf value is observed in the range of 0.05 < x < 0.4, and the most deteriorated Qf value of 70 500 GHz is located at x = 0.2. The reasons for the variation of Qf value of Sr 1+ x La 1− x Al 1− x Ti x O 4 solid solution can be interpreted by several factors as follows: Considering the K 2 NiF 4 structure of Sr 1+ x La 1− x Al 1− x Ti x O 4 solid solution, the size adaptability between perovskite layer and rocksalt layer is usually reflected by the tolerance factor t 21−24. where , , , , and are the effective radii of Sr 2+ , La 3+ , Al 3+ , Ti 4+ , and O 2− , respectively .…”

Electrical properties of the Sr2Ru1−xTixO4 solid solutions

“…[1][2][3] This structure possesses ABO 3 (B = transition metal ion), perovskite-type, layers between rock-salt A-O layers, B-O-B interactions occurring only in the ab plane have been investigated. 4 The K 2 NiF 4 -type structure; Sr 2 RuO 4 has also been investigated as a spin-triplet unconventional superconductor with T c ∼ −271.66 • C. 5 Recently, it has been reported that the Sr 2 Ru 1−x Ti x O 4 solid solution, with the substitution of non-magnetic Ti 4+ (3d 0 ) for Ru 4+ (4d 4 ) in Sr 2 RuO 4 , changes from spin-triplet superconductivity to magnetic ordering for x ≥ 0.25. 6,7 Polycrystalline samples of Sr 2 Ru 1−x Ti x O 4 with composition 0 ≤ x ≤ 1, on the other hand, have been synthesized and the electrical resistivities determined at room temperature.…”

Investigation of structural, magnetic and electric transport properties of half-doped chromium manganites La0.3R0.2Sr0.5Mn0.5Cr0.5O3 (R=La, Nd, Sm, and Gd)

“…The rotation of the MnO 6 octahedra is governed by the tolerance factor (t) [44,45], which is defined as With a view to understand the electrical and magnetic properties with the variation of A-site ionic radii, the average A-site ionic radii 〉 〈 A r and size variance factor ( 2 σ ) have been calculated from the standard ionic radii [46] of nine-fold coordination and are given in Table 2. The variation 2 σ with 〉 〈 A r is shown in Fig.2.…”