在2H-矿相关氧化物中,相位过渡,磁矩和价值不成比例之间有着引人注目的相互联系
Qingbiao Zhao1, Jacques Darriet, Myung-Hwan Whangbo
1Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA.
Journal of the American Chemical Society
|December 7, 2011
概括
本研究详细介绍了Sr(5) Co(4) O(12) 和Sr(6) Co(5) O(15) 氧化物的晶体结构和磁性特性. Sr{5) Co{4) O{12) 呈现与价值不成比例和Jahn-Teller扭曲相关的相位过渡.
科学领域:
- 材料科学 材料科学 材料科学
- 固态化学 固态化学
- 磁力学 磁力学 是一种
背景情况:
- 2H-矿相关氧化物是一种具有复杂结构和有趣电子特性的材料类.
- 刚氧化物,如Sr5) Co4) O12和Sr6) Co5) O15,属于这个家族,需要进一步调查.
研究的目的:
- 合成和描述两个新型的合金氧化物:Sr5) Co4) O12和Sr6) Co5) O15.
- 确定晶体结构并研究这些化合物的磁性特性.
- 为了阐明电荷不成比例和Sr{5) Co{4) O{12}中的相变.
主要方法:
- 单晶X射线衍射用于结构确定.
- 测量磁性易感性 (韦斯温度,磁性异构性).
- 特定热量,西贝克系数和电导率测量.
- 债券价值总和计算.
主要成果:
- 6Co5O15在R32空间群结晶,与6Rh5O15具有同结构,并且表现出主导性的反铁磁相互作用,没有远程顺序.
- 5) 4) 12) 在P-3c1空间群结晶,在170 K.左右经历结构转变.
- 在Sr{5) Co{4) O{12) 中的转变与价值不成比例,Jahn-Teller扭曲以及磁矩和异性变化有关.
结论:
- 该研究成功地合成和表征了Sr(5) Co(4) O(12) 和Sr(6) Co(5) O(15),提供了对它们的结构和磁性行为的见解.
- Sr{5) Co{4) O{12) 显示出由电子和结构因素驱动的独特相位过渡,突出了其在相关电子系统的进一步研究的潜力.
- 这两种化合物都表现出复杂的磁性相互作用,其中Sr(5) Co(4) O(12) 显示出显著的磁性异质性.
相关概念视频
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
02:58Crystal Field Theory - Octahedral Complexes
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
01:28Phase Diagrams of Ternary Systems
Consider a ternary system, which is composed of three components: water (W), ethanoic acid (E), and trichloromethane (T). Here, Ethanoic acid (E) is fully miscible with both water (W) and trichloromethane (T), meaning it can mix entirely with either of them. However, water and trichloromethane have partial miscibility, meaning they can only mix to a certain extent, beyond which two separate phases will form.The phase diagram of a ternary system is represented as an equilateral triangle, where...
01:19Phase Diagram
The phase of a given substance depends on the pressure and temperature. Thus, plots of pressure versus temperature showing the phase in each region provide considerable insights into the thermal properties of substances. Such plots are known as phase diagrams. For instance, in the phase diagram for water (Figure 1), the solid curve boundaries between the phases indicate phase transitions (i.e., temperatures and pressures at which the phases coexist).
01:24Phase Diagram
A phase diagram is a graphical representation of the physical states of a substance under different conditions of temperature and pressure. It shows the boundaries between solid, liquid, and gas phases and the conditions at which these phases coexist in equilibrium. An area in a phase diagram represents a single phase, whereas lines or phase boundaries represent the equilibrium between two phases.In the phase diagram of water, the boundary line between the solid and liquid states illustrates...