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Single crystal growth of spin ladders and related compounds at high pressure.

自旋梯和相关化合物在高压下的单晶生长。

基本信息

批准号：
11640347
负责人：
AZUMA Masaki
金额：
$ 2.3万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11640347/
关键词：
Spin ladder compounds Spin gap High pressure synthesis Synchrotron radiation βX-ray diffraction Single crystals 高圧合成法高温超伝導体圧力誘起構造相転移

项目摘要

High pressure (HP) synthesis is a powerful technique to search for new materials. We have discovered many low dimensional magnets such as high-T_c superconductors and spin ladder compounds using this technique. Generally speaking, however, it used to be almost impossible to obtain single crystal samples of these high-pressure phases because of the lack of the information about the HP-HT (high temperature) reactions. High energy, high flux X-ray from synchrotron radiation enabled us to observe such a reaction in a HP cell even if the sample is in a gold or a platinum capsule. The melting point of the samples with various kinds of flux were determined and such information was applied for the single crystal growth.1. HP phase of (VO)_2P_2O_7 : S =1/2 one dimensional alternating exchange antiferromagnet with a spin gap. The powder XRD data collected with a cubic-anvil type high-pressure apparatus installed at BL14B1 of Spring-8 clearly showed the transformation from the AP phase to the HP … More phase at 3GPa and 500゜C and the melting at 1150゜C.Single crystals were obtained by slowly cooling the melt from 1300゜C to 700゜C in 60h at 3GPa using a in-house HP apparatus.2. Ca_<2-x>Na_xCuO_2Cl_2 : High Tc superconductor with chlorine instead of apical oxygen. It is an ideal compound for photoemission and STM measurements because a) easy to cleave (fresh CuO_2 plane is available), b) samples from insulator to doped superconductor are available, c) there is no orthorhombic distortion at low temperature, d)it has no modulation. Mixtures of Ca_2CuO_2Cl_2, NaClO_4 and NaCl were slowly cooled from 1250゜C to 1050゜C at various pressures to obtain plate-like crystals. NaClO_4 worked as flux, Na source and oxygen generator. The Na content could be tuned by changing the pressure during the crystal growth.3. CaFeO_3 : a distorted perovskite (GdFeO_3 type) with unusual Fe^<4+> ion which shows charge disproportionation to Fe^<3+> and Fe^<5+> below room temperature. A mixture of KClO_4, NaClO_4 and CaCl_2 was used as flux and oxygen generator. Less

高压（HP）合成是寻找新材料的强大技术。我们使用这种技术发现了许多低维磁体，例如高温超导体和自旋梯化合物。然而，一般来说，由于缺乏有关 HP-HT（高温）反应的信息，过去几乎不可能获得这些高压相的单晶样品。来自同步加速器辐射的高能、高通量 X 射线使我们能够在 HP 池中观察到这种反应，即使样品位于金或铂胶囊中。测定了不同助熔剂样品的熔点，并将该信息应用于单晶生长。 1． (VO)_2P_2O_7 的 HP 相：S =1/2 具有自旋间隙的一维交替交换反铁磁体。使用安装在 Spring-8 BL14B1 的立方砧型高压装置收集的粉末 XRD 数据清楚地显示了在 3GPa 和 500゜C 下从 AP 相到 HP … More 相的转变以及在 1150゜C 熔化。通过使用内部设备在 3GPa 下在 60 小时内将熔体从 1300゜C 缓慢冷却到 700゜C 获得单晶。惠普仪器.2. Ca_<2-x>Na_xCuO_2Cl_2：用氯代替顶端氧的高Tc超导体。它是光电发射和 STM 测量的理想化合物，因为 a) 易于劈裂（可以获得新鲜的 CuO_2 平面），b) 可以获得从绝缘体到掺杂超导体的样品，c) 低温下不存在正交变形，d) 没有调制。将Ca_2CuO_2Cl_2、NaClO_4和NaCl的混合物在不同压力下从1250゜C缓慢冷却至1050゜C以获得板状晶体。 NaClO_4作为助熔剂、Na源和氧气发生器。 Na含量可以通过改变晶体生长过程中的压力来调节。3． CaFeO_3 ：一种扭曲的钙钛矿（GdFeO_3 型），具有不寻常的 Fe^<4+> 离子，在室温下显示出电荷歧化为 Fe^<3+> 和 Fe^<5+>。采用KClO_4、NaClO_4和CaCl_2的混合物作为熔剂和氧气发生器。较少的