Nuclear acoustic resonance in a liquid metal

Reusche, M.J.; Unterhorst, E. J.

doi:10.1016/0375-9601(75)90445-4

Cited by 5 publications

(1 citation statement)

References 6 publications

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“…If v, is the electron velocity averaged over the Fernii surface, dgldt is given by where e, is the effective mass density of the electrons, pi the mass density of the ions, and e, = ,oe + p i . Since the electric current density is defined by where the charge density of the electrons is designated by qe and that of the ions by q,, by aid of simple algebraic operations and r], + qi = 0 it can be shown that (4) is equivalent to As j can be replaced by qev, without altering t,he value of P(t), (7) demonstrates that this part of external energy is transferred into the lattice (formed by the ions) via the electron-ion interaction.…”

Section: Theory Of Dipole Narmentioning

confidence: 99%

Nuclear Acoustic Resonance Absorption and Dispersion in Vanadium via Coupling to the Magnetic Dipole Moment

Müller¹,

Schanz²,

Fischer³

et al. 1977

Physica Status Solidi (b)

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The first observation of both NAR absorption and NAR dispersion in a single crystal vanadium due to the coupling of longitudinal acoustic waves to the magnetic dipole moment of the V5* nuclei is reported. The experiment is performed in the temperature range of 5 to 294 K. The obRerved angular dependence and NAR line shapes are in good agreement with the formvlas derived in this paper.Es wird uber den ersten erfolgreichen Nachweis von NAR-Absorptions-und NAR-Dispersionssignalen in einem Vanadiumeinkristall mit longitudinalem Schall berichtet. Die Kopplung des Schallfeldes mit den VSl-Kernen erfolgt iiber die Wechselwirkung mit dem magnetischen Kerndipolmoment. Die Messungen werden im Temperaturbereich von 5 bis 294 K durchgefuhrt. Die beobachtete Winkelabhangigkeit und NAR-Linienform sind in guter ubereinstimmung mit den in dieser Arbeit abgeleiteten Formeln. IntrodudionI n conducting materials in the presence of a dc magnetic field B,, a sound wave produces a n electric current which results in an internal electromagnetic field oscillating coherently with the sound wave [l]. I n metals an acoustic wave therefore may induce nuclear magnetic dipole transitions which are detected through a change in ultrasonic phase velocity and attenuation. This coupling mechanism has been observed in several pure metals [2 to 81 and generally the resulting NAR signals are found to be asymmetric. This asymmetry has been expressed by several authors in terms of the real and imaginary part of the complex nuclear magnetic spin susceptibility x. The actual expressions [9 to 181, however, differ markedly in their dependencies on x' and f ' and the final result of a comprehensive theory [ 161 is not in agreement with experiment if x is interpreted as conventional nuclear magnetic spin susceptibility observed in NMR. Furthermore we feel that most of the actual derivations of the given formulas do not reveal the physics. To elucidate the physical origin of the terms causing the observed asymmetry of the NAR lines, we choose a model [19] where the real metal is substituted by a gas of conduction electrons embedded in a background of positive ions and the interaction between the charged particles is replaced by the interaction with a self-consistent electromagnetic field derived from Maxwell's equations. When an acoustic wave propagates in the metal, the ions will experience oscillatory motions which are screened by the condution electrons. I n the presence of an external magnetic field, however, the screening is not quite complete so that there is a small resultant current density j. Hence, in addition to the ordinary elastic force density, the Lorentz force density

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Section: Theory Of Dipole Narmentioning

confidence: 99%

Nuclear Acoustic Resonance Absorption and Dispersion in Vanadium via Coupling to the Magnetic Dipole Moment

Müller¹,

Schanz²,

Fischer³

et al. 1977

Physica Status Solidi (b)

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Nuclear acoustic resonance in liquid gallium

Unterhorst

Müller

Schanz

1977

Physica Status Solidi (b)

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T o date two relevant interaction mechanisms a r e known which can couple acoustic energy to a nuclear spin system. One is the magnetic dipole interaction with the sound induced rf magnetic field which, in the presence of a dc magnetic field go, may be considerably large in conductors, the other one is the familar quadrupole interaction with the sound induced dynamic electric field gradient (DEFG). However, nuclear acoustic resonance (NAR) in liquid metals, first observed in liquid Ga /1/, only can take place via the magnetic dipole interaction since in liquids with law viscosity it i s impossible /2/ to generate a DEFG whose frequency distribution i s smaller than the width of the Zeeman levels of the nuclei. This is due to the fact that the DEFG depends on the distance R.. This i s a marked difference compared to the sound induced electromagnetic field in conductors which above all depends on the ultrasonic displacement field and not on the distance g..(t) between the particles. As the total displacement field is a superposition of the thermal and the ultrasonic displacement field, in consequence of f i x w e l l ' s equations the resulting electromagnetic field may be written as a s u m of a coherent part (oscillating coherently with the sound wave) and an incoherent part causing motional narrowing. Thus, provided that the diffusion length during the nuclear spin relaxation time i s small compared to the ultrasonic wavelength, it should be possible t o observe NAR in liquid metals. On the other hand, the sound induced rf magnetic field is an internal field and therefore NAR via the coupling to the nuclear magnetic dipole moment can be regarded a s NMR in the interior of a conductor.

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Nuclear acoustic resonance in metals

Müller

Bartell

1979

Z Physik B

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Nuclear acoustic resonance in a liquid metal

Cited by 5 publications

References 6 publications

Nuclear Acoustic Resonance Absorption and Dispersion in Vanadium via Coupling to the Magnetic Dipole Moment

Nuclear Acoustic Resonance Absorption and Dispersion in Vanadium via Coupling to the Magnetic Dipole Moment

Nuclear acoustic resonance in liquid gallium

Nuclear acoustic resonance in metals

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