Spin-Echo and Free-Induction-Decay Measurements in Pure Fe and Fe-Rich Ferromagnetic Alloys: Domain-Wall Dynamics

1967 ◽  
Vol 162 (2) ◽  
pp. 496-509 ◽  
Author(s):  
Mary Beth Stearns
Keyword(s):  
Domain Wall ◽  
Free Induction Decay ◽  
Spin Echo ◽  
Ferromagnetic Alloys ◽  
Domain Wall Dynamics ◽  
Free Induction

Advancement and validation of surface nuclear magnetic resonance spin-echo measurements of T2

Geophysics ◽  
2014 ◽  
Vol 79 (2) ◽  
pp. EN15-EN23 ◽  
Author(s):  
Elliot Grunewald ◽  
Rosemary Knight ◽  
David Walsh
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Pore Size ◽  
Free Induction Decay ◽  
Field Experiments ◽  
Spin Echo ◽  
Coarse Grained ◽  
Background Magnetic Field ◽  
Free Induction ◽  
Nuclear Magnetic

Obtaining reliable estimates of hydrogeologic properties from nuclear magnetic resonance (NMR) measurements requires the ability to measure NMR relaxation parameters that are most sensitive to pore-scale geometry. Conventional surface NMR measurements of the free induction decay yield accurate estimates of the relaxation time parameter [Formula: see text], but it has been shown that this parameter can exhibit limited sensitivity to pore size and permeability. We evaluated an improved surface-NMR scheme that uses spin-echo signals to estimate the more robust and readily usable relaxation parameter [Formula: see text]. The acquisition methodology builds upon previous spin-echo schemes and incorporates robust phase-cycling procedures, which remove responses that can potentially interfere with the echo signals. A new two-stage linear inversion was used to derive quantitative estimates of [Formula: see text] with depth. The method was evaluated in two field experiments at sites in the central and western United States. At one site, NMR logging measurements in a nearby borehole provided the first opportunity to compare [Formula: see text]-values estimated by surface NMR to [Formula: see text]-values determined from the logging data. The surface and logging results showed very close agreement at depths where [Formula: see text] is long, but echoes cannot be detected from depths where [Formula: see text] is shorter than the minimum echo time. As anticipated, we found that [Formula: see text] derived from spin echoes was generally much longer than [Formula: see text], derived from the free induction decay. We explain the observed differences by considering the magnitude of inhomogeneity in the background magnetic field. We note that [Formula: see text] exhibited greater variation and sensitivity to pore size than [Formula: see text] in coarse-grained materials, while [Formula: see text] provided greater sensitivity in fine-grained materials where no echo signal was detected. Given these complementary advantages of [Formula: see text] and [Formula: see text] measurement, we advocate adoption of a framework combining spin-echo and free induction decay data to improve characterization of groundwater aquifers.

scholarly journals Free Induction Decay and Spin Echo Signals from Spin Triplet States of Axially Asymmetric Objects in Single Crystals in Zero Constant Magnetic Field:

2020 ◽  
Vol 5 (7) ◽  
pp. 813-821
Author(s):  
Nathalie P. Fokina ◽  
Maia O. Elizbarashvili
Keyword(s):  
Magnetic Field ◽  
Single Crystals ◽  
Constant Magnetic Field ◽  
Free Induction Decay ◽  
Spin Echo ◽  
Zero Field ◽  
Triplet States ◽  
Free Induction ◽  
Spin Triplet ◽  
Axially Asymmetric

Anisotropic dynamics of the spin triplet states (STSs) in single crystals with the zero field splitting (ZFS) of their levels by the axially asymmetric Hamiltonian is investigated in zero constant magnetic field (ZF) under the action of the canonically oriented varying magnetic fields. The equations of motion for single transition operators (STOs) corresponding to the definite transition of ZFS are derived.  The obtained equations written in terms of one averaged equation for STO vector appeared to be a particular case (for STS) of the universal equation of Feynman et al, which is valid for any kind of perturbation affecting only two levels of any quantum mechanical system. As well as that, our equation is analogous to the Bloch equation without decay for the usual magnetization components of the Zeeman system in a constant magnetic field and a transverse to it varying field. This statement is valid, if the population probabilities of the corresponding levels of STS are not artificially equalized. At that, the motion of the observable macroscopic sample magnetization, which follows from our equations, has quite different character. Here, in terms of this magnetization the signals of the free induction decay and of the two-pulse spin echo are calculated in ZF.  

Domain wall dynamics: Growth laws, localized structures and stable droplets

2007 ◽  
Vol 146 (1) ◽  
pp. 71-86 ◽  
Author(s):  
D. Gomila ◽  
P. Colet ◽  
M. S. Miguel ◽  
G.-L. Oppo
Keyword(s):  
Domain Wall ◽  
Domain Wall Dynamics ◽  
Localized Structures ◽  
Growth Laws
Sign in / Sign up

Export Citation Format

Share Document