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相关概念视频

Spin–Spin Coupling Constant: Overview01:08

Spin–Spin Coupling Constant: Overview

862
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
862
NMR Spectroscopy: Spin–Spin Coupling01:08

NMR Spectroscopy: Spin–Spin Coupling

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The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved...
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Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

940
Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
940
Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

1.0K
Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the...
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Spin–Spin Coupling: One-Bond Coupling01:17

Spin–Spin Coupling: One-Bond Coupling

922
Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
922
Double Resonance Techniques: Overview01:12

Double Resonance Techniques: Overview

178
Double resonance techniques in Nuclear Magnetic Resonance (NMR) spectroscopy involve the simultaneous application of two different frequencies or radiofrequency pulses to manipulate and observe two distinct nuclear spins. One important application of double resonance is spin decoupling, which selectively suppresses coupling with one type of nucleus while observing the NMR signal from another nucleus, simplifying the spectrum and enhancing resolution.
Spin decoupling is usually achieved by...
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在Py/FeMn接口上进行交换合诱导的旋转动态缓冲调制.

Mingming Tian1, Qian Chen1, Wei Jiang1

  • 1Key Laboratory of Quantum Materials and Devices of Ministry of Education, School of Physics, Southeast University, Nanjing 211189, China.

ACS applied materials & interfaces
|February 26, 2025
PubMed
概括

接口交换合显著增强了-铁 (Py) /铁- (FeMn) 双层中的自旋动态阻尼,这对于自旋电子设备至关重要. 这种由交换合驱动的效应,比旋转送更能增强阻尼.

关键词:
交换合接口 交换合接口磁力学动力学是一种磁力学动力学.旋转动态减缓 旋转动态减缓旋转 放松 放松旋转电子技术 (spintronics) 是一个技术.

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科学领域:

  • 这就是Spintronics.
  • 材料科学 材料科学 材料科学
  • 凝聚物质物理学 凝聚物质物理学

背景情况:

  • 旋转动态缓对于先进的磁性内存,传感器和逻辑系统至关重要.
  • 接口反铁磁交换合是旋转式异构结构中的一个关键现象.

研究的目的:

  • 为了研究Ni80Fe20(Py) /Fe50Mn50(FeMn) 双层的磁力学.
  • 阐明界面交换合与旋转送在旋转动态阻尼中的作用.

主要方法:

  • 系统地研究不同厚度的FeMn二层Py/FeMn.
  • 引入一个铜 (Cu) 间隔器来解磁层.
  • 分析旋转动态阻尼和旋转效应.

主要成果:

  • 对于FeMn厚度> 5nm,会出现一个界面交换偏差场,显著增加旋转动态缓.
  • 引入一个Cu间隔器可以抑制交换偏差并减少阻尼,由于旋转抽而导致的轻微增加.
  • 在Py/Cu/FeMn三层中估计的界面旋转混合电导率为3.44nm-2,与FeMn的弱旋转轨道合有关.
  • FeMn插入显示了短的旋转扩散长度,并证实了接口交换合在减压增强中的主导作用.

结论:

  • 接口交换合是Py/FeMn双层中增强旋转动态阻尼的主要驱动因素,超过了旋转效应.
  • 在Py/FeMn接口上的交换合促进了旋转放松,并阻碍了旋转传输.
  • 将抗铁磁材料与交换合接口集成,为增强高频自旋电子应用提供了一个有前途的途径.