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New NMR Techniques for the Study of Catalysis
Published in Alexis T. Bell, Alexander Pines, NMR Techniques in Catalysis, 2020
Waclaw Kolodziejski, Jacek Klinowski
Spectral spin diffusion in the solid state involves simultaneous flipflop transitions of dipolar-coupled spins with different resonance frequencies [1,39,63-76], whereas spatial spin diffusion transports spin polarization between spatially separated equivalent spins. In this review we deal only with the first case. The interaction of spins undergoing spin diffusion with the proton reservoir provides compensation for the energy imbalance (extraneous spins mechanism) [68,70,73,74]. Spin diffusion results in an exchange of magnetization between the nuclei responsible for resolved NMR signals, which can be conveniently detected by observing the relevant cross-peaks in the 2D spin-diffusion spectrum [63-65]. This technique, formally analogous to the NOESY experiment in liquids, is already well established for solids and can also be applied to the study of catalysts.
Spin Transport in Hybrid Nanostructures
Published in Evgeny Y. Tsymbal, Igor Žutić, Spintronics Handbook: Spin Transport and Magnetism, Second Edition, 2019
Saburo Takahashi, Sadamichi Maekawa
The spin-dependent transport in hybrid nanostructures is currently of great interest, particularly in the emergence of new phenomena as well as the potential applications to spintronic devices [1–6]. Recent experimental and theoretical studies have demonstrated that the spin-polarized carriers injected from a ferromagnet (F) into a nonmagnetic material (N), such as a normal conducting metal, semiconductor, and superconductor, create nonequilibrium spin accumulation and spin current over the spin diffusion length in the range from nanometers to micrometers. Efficient spin injection and detection and creation of large spin current, spin accumulation, and spin transfer are key factors in utilizing the spin degrees of freedom of carriers as a new functionality in spintronic devices [7, 8].
Spin Injection, Accumulation, and Relaxation in Metals
Published in Evgeny Y. Tsymbal, Žutić Igor, Spintronics Handbook: Spin Transport and Magnetism, Second Edition, 2019
The physics of spin accumulation and spin diffusion are closely related to the principles of electron spin resonance, and there are similarities in the techniques for measuring spin-diffusion lengths and spin-relaxation times. Beginning with a reminder of basic definitions, the magnetic dipole moment of a conduction electron is related to its spin-angular momentum, S→, by μ→=−gemcS→,
General theory of light propagation and triplet generation for studies of spin dynamics and triplet dynamic nuclear polarisation
Published in Molecular Physics, 2023
Yifan Quan, Nemanja Niketic, Jakob M. Steiner, Tim R. Eichhorn, W. Tom Wenckebach, Patrick Hautle
Furthermore, our model assumes that spin diffusion is fast enough to polarise the nuclei between the pentacene molecules, but too slow to change the homogeneity of polarisation over the entire crystal length. In our crystals the pentacene number density is typically in the order of m so the distance between the pentacene molecules is roughly nm. The spin diffusion time is given by , where r is the distance and D is the spin diffusion constant, which in the order of cms [36]. Spin diffusion covers a distance of nm in about 1.3 ms, which is comparable to our typical pulse repetition time of 1 ms. Thus the spin diffusion is fast enough to spread the polarisation between the pentacene molecules, while it is not able to homogenise polarisation on a macroscopic scale, e.g. it takes about 1000 h for spin diffusion to cover r = 0.1 mm. This justifies our assumption.
Recent advances in two-dimensional ferromagnetism: strain-, doping-, structural- and electric field-engineering toward spintronic applications
Published in Science and Technology of Advanced Materials, 2022
Sheng Yu, Junyu Tang, Yu Wang, Feixiang Xu, Xiaoguang Li, Xinzhong Wang
Electric field can also effectively improve the spin transport of 2D magnets via reducing spin relaxation and enhancing magnetoresistance, exhibiting a substantial potential for the practical application of spin valve device. Avsar et al. [131] fabricated a semiconducting spin valve device by encapsulating ultrathin black phosphorus (~5 nm) into hexagonal boron nitride atomic layers. They observed a long spin relaxation time of ~4 ns with spin relaxation length of ~6 µm by measuring Hanle spin precession. Liang et al. [132] showed the gate-tunable electrical spin-valve device with magnetoresistance of 1.1% in a multilayer MoS2 semiconducting channel on a ferromagnetic Co/MgO electrode by using a two-terminal configuration. They found that the spin relaxation is largely prevented with an enhanced spin diffusion length of 235 nm. Yang et al. [133] theoretically investigated the spin transport in spin-valve device based on Fe3GeTe2 monolayer where a high magnetoresistance of ~390% was obtained and can be significantly increased to ~510% under the electric gates.
Comparative study on water structures of poly(tetrahydrofurfuryl acrylate) and poly(2-hydroxyethyl methacrylate) by nuclear magnetic resonance spectroscopy
Published in Journal of Biomaterials Science, Polymer Edition, 2021
Akira Mochizuki, Yoshiki Oda, Yuko Miwa
As solution NMR has a much higher resolution than solid-state NMR, we attempted to apply it to analyze water in PMEA, with poly(butyl acrylate) (PBA) as a control that has poorer blood compatibility without any organic solvent, and concluded that solution NMR is valuable for the analysis of the water structure in polymers [18]. In the investigation, we found that two types of water exist in hydrated PMEA: water molecules with low mobility, appearing at a higher magnetic field (referred to as “upfield”) area (3–4 ppm), and those with high mobility, appearing at a lower magnetic field (referred as “downfield”) area (4–5 ppm). In contrast, PBA has a single type of water structure appearing in the downfield area. Thus, it was concluded that the blood compatibility depends on water molecules appearing upfield. Based on these findings, we applied this method to analyze the hydrated PTHFA and PHEMA to obtain further information on the water structure relating to the blood compatibility. In the investigation, we used D2O as water instead of hydrogen oxide (H2O), as H2O has several drawbacks in the NMR analysis; the spectral overlap with the polymer peaks and the complicated 1H relaxation properties such as intermolecular and dipole–dipole coupling as well as cross-relaxation and spin diffusion between water and polymer protons. In contrast, the 2H nuclei relaxation process is simple, arising from intramolecular quadrupole coupling and reflecting local dynamics of individual water molecules [19, 20].