Glazkova Yana S, Terada Noriki, Matsushita Yoshitaka, Katsuya Yoshio, Tanaka Masahiko, Sobolev Alexey V, Presniakov Igor A, Belik Alexei A
International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS) , Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
Department of Chemistry, Lomonosov Moscow State University , Leninskie Gory, 119992 Moscow, Russia.
Inorg Chem. 2015 Sep 21;54(18):9081-91. doi: 10.1021/acs.inorgchem.5b01472. Epub 2015 Aug 31.
We synthesize CdMn7O12 and SrMn7-xFexO12 (x = 0, 0.08, and 0.5) perovskites under high pressure (6 GPa) and high temperature (1373-1573 K) conditions and investigate their structural, magnetic, dielectric, and ferroelectric properties. CdMn7O12 and SrMn7O12 are isostructural with CaMn7O12: space group R3̅ (No. 148), Z = 3, and lattice parameters a = 10.45508(2) Å and c = 6.33131(1) Å for CdMn7O12 and a = 10.49807(1) Å and c = 6.37985(1) Å for SrMn7O12 at 295 K. There is a structural phase transition at 493 K in CdMn7O12 and at 404 K in SrMn7O12 to a cubic structure (space group Im3̅), associated with charge ordering as found by the structural analysis and Mössbauer spectroscopy. SrMn6.5Fe0.5O12 crystallizes in space group Im3̅ at 295 K with a = 7.40766(2) Å and exhibits spin-glass magnetic properties below 34 K. There are two magnetic transitions in CdMn7O12 with the Néel temperatures TN2 = 33 K and TN1 = 88 K, and in SrMn7O12 with TN2 = 63 K and TN1 = 87 K. A field-induced transition is found in CdMn7O12 from about 65 kOe, and TN2 = 58 K at 90 kOe. No dielectric anomalies are found at TN1 and TN2 at 0 Oe in both compound, but CdMn7O12 exhibits small anomalies at TN1 and TN2 at 90 kOe. In pyroelectric current measurements, we observe large and broad peaks around magnetic phase transition temperatures in CdMn7O12, SrMn7O12, and SrMn6.5Fe0.5O12; we assign those peaks to extrinsic effects and compare our results with previously reported results on CaMn7O12. We also discuss general tendencies of the AMn7O12 perovskite family (A = Cd, Ca, Sr, and Pb).
我们在高压（6吉帕）和高温（1373 - 1573开尔文）条件下合成了钙钛矿CdMn7O12和SrMn7 - xFexO12（x = 0、0.08和0.5），并研究了它们的结构、磁性、介电和铁电性质。CdMn7O12和SrMn7O12与CaMn7O12同构：空间群为R3̅（编号148），Z = 3，295 K时CdMn7O12的晶格参数a = 10.45508(2) Å，c = 6.33131(1) Å，SrMn7O12的晶格参数a = 10.49807(1) Å，c = 6.37985(1) Å。CdMn7O12在493 K、SrMn7O12在404 K发生结构相变，转变为立方结构（空间群Im3̅），这与结构分析和穆斯堡尔谱所发现的电荷有序有关。SrMn6.5Fe0.5O12在295 K时结晶于空间群Im3̅，a = 7.40766(2) Å，在34 K以下表现出自旋玻璃磁性。CdMn7O12有两个磁转变，奈尔温度TN2 = 33 K，TN1 = 88 K；SrMn7O12的TN2 = 63 K，TN1 = 87 K。在CdMn7O12中发现约65千奥斯特的场致转变，90千奥斯特时TN2 = 58 K。两种化合物在0奥斯特时TN1和TN2处均未发现介电异常，但CdMn7O12在90千奥斯特时TN1和TN2处表现出小的异常。在热释电电流测量中，我们在CdMn7O12、SrMn7O12和SrMn6.5Fe0.5O12的磁相变温度附近观察到宽而大的峰；我们将这些峰归因于外在效应，并将我们的结果与先前报道的CaMn7O12的结果进行比较。我们还讨论了AMn7O₁₂钙钛矿家族（A = Cd、Ca、Sr和Pb）的一般趋势。
