Topic
Nuclear quadrupole resonance
About: Nuclear quadrupole resonance is a research topic. Over the lifetime, 3531 publications have been published within this topic receiving 38801 citations. The topic is also known as: Nuclear quadrupole resonance spectroscopy & NQR.
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TL;DR: It is found that the quasi-steady state magnetization exhibits dips at particular frequency offsets and more interestingly that its decay rate T(2 eff) (-1) exhibits similar dips (slower decay) at the same frequency offsets.
Abstract: In this work, we investigate off-resonance effect on the (14)N nuclear quadrupole resonance magnetization decay during the spin-lock spin-echo pulse sequence (SLSE). The compound chosen for this study is paranitrotoluene with a single (14)N site, which represents a suitable simplified model for the explosive trinitrotoluene with six nonequivalent (14)N sites. We find that the quasi-steady state magnetization exhibits dips at particular frequency offsets and more interestingly that its decay rate T(2 eff) (-1) exhibits similar dips (slower decay) at the same frequency offsets. The coexistence of dips is very important for applications where the primary use of the SLSE sequence is to increase the signal-to-noise ratio, as longer sampling times compensate for small magnetization values. A theory explaining both observations is presented which includes homonuclear dipolar interactions and spin coupling to the lattice. We show that the homonuclear dipolar interaction contributes only 20% to the total magnetization decay rate, while spin-lattice coupling is the dominant mechanism.
25 citations
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TL;DR: It is shown that Ta NQR is a novel probe for the bulk Weyl fermions and their excitations as well as the magnetic excitations at the Weyl nodes with temperature-dependent orbital hyperfine coupling.
Abstract: The ^{181}Ta quadrupole resonance [nuclear quadrupole resonance (NQR)] technique is utilized to investigate the microscopic magnetic properties of the Weyl semimetal TaP. We find three zero-field NQR signals associated with the transition between the quadrupole split levels for Ta with I=7/2 nuclear spin. A quadrupole coupling constant, ν_{Q}=19.250 MHz, and an asymmetric parameter of the electric field gradient, η=0.423, are extracted, in good agreement with band structure calculations. In order to examine the magnetic excitations, the temperature dependence of the spin-lattice relaxation rate (1/T_{1}T) is measured for the f_{2} line (±5/2↔±3/2 transition). We find that there exist two regimes with quite different relaxation processes. Above T^{*}≈30 K, a pronounced (1/T_{1}T)∝T^{2} behavior is found, which is attributed to the magnetic excitations at the Weyl nodes with temperature-dependent orbital hyperfine coupling. Below T^{*}, the relaxation is mainly governed by a Korringa process with 1/T_{1}T=const, accompanied by an additional T^{-1/2}-type dependence to fit our experimental data. We show that Ta NQR is a novel probe for the bulk Weyl fermions and their excitations.
25 citations
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TL;DR: A novel approach which can detect NQR signals of very low SNRs in such scenarios, by combining a stochastic resonance framework and neural network theory, and can also be effective in cases where both noise and radio frequency interference are strong relative to the N QR response.
25 citations
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25 citations
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TL;DR: In this article, the ferromagnetic and superconducting transition in UCoGe was studied using both nuclear magnetic resonance and nuclear quadrupole resonance (NQR) studies.
Abstract: Co nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) studies were carried out for the recently discovered UCoGe, in which the ferromagnetic and superconducting (SC) transition...
25 citations