Nuclear-Acoustic-Resonance Absorption and Dispersion in Aluminum

Leisure, R. G.; Hsu, D. K.; Seiber, B. A.

doi:10.1103/physrevlett.30.1326

Cited by 17 publications

(3 citation statements)

References 14 publications

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“…The lineshape of the attenuation anomaly passing T N1 is different from the symmetric Lorentzian function previously observed in conventional antiferromagnets and attributed to relaxation effects [14]. Figure 4 shows an increase and a following decrease of α that resembles observations in acoustic nuclear resonance [21]. Here, however, it is due to the strongly dispersing sound pulse and the rapidly changing sound velocity in the critical regime.…”

Section: Resultsmentioning

confidence: 64%

On the Limits of Indetermination and on the Set of Limit Functions of Series in the Walsh System

Šaginjan¹

1974

Math. USSR Sb.

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The magnetic phase diagram of multiferroic MnWO 4 is studied in magnetic fields up to 60 T using sound velocity and sound attenuation measurements. Anomalies are observed at temperatures T N1 = 7.6 K, T N2 = 12.6 K and T N3 = 13.6 K that separate commensurate antiferromagnetic (AF1) to helical AF2 and commensurate AF3 to paramagnetic phases, respectively. The anomalies are significantly different and shed light on the spin-phonon coupling and evolution of the various order parameters in this multiferroic material. For temperatures below T N2 pronounced field hysteresis effects are also observed in the sound velocity, indicating field-induced transformations. In the temperature dependence of the attenuation we observe anomalies distinctively different from the usual maxima related to relaxation effects. They are attributed to the combination of dispersion effects due to domain walls and the discontinuously changing sound velocity. In total, six different magnetic phases, at various temperatures and fields including a novel high-field phase, are revealed and analyzed.

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Section: Resultsmentioning

confidence: 64%

On the Limits of Indetermination and on the Set of Limit Functions of Series in the Walsh System

Šaginjan¹

1974

Math. USSR Sb.

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“…The high Q values of many resonance lines will enhance sensitivity. High Q values in conventional ultrasonic standing wave measurements have provided enough sensitivity to detect ultrasonically excited electron spin resonance [27] and nuclear magnetic resonance [28], which are extremely small effects. Motion with a rate comparable to the ultrasonic frequency leads to relaxational attenuation.…”

Section: Effects Of Dissipationmentioning

confidence: 99%

Resonant ultrasound spectroscopy

Leisure

Willis

1997

J. Phys.: Condens. Matter

279

151

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Resonant ultrasound spectroscopy (RUS) involves the study of the mechanical resonances of solids. The resonant response of a particular object depends on its shape, elastic constants, crystallographic orientation, density, and dissipation. It is possible to obtain the complete elastic constant matrix of relatively low-symmetry materials from a RUS spectrum on a single small sample (<1 mm 3 ). The measurement and the computation of the RUS spectra of solids are reviewed. Several examples of the use of the technique are discussed. Contents 1 Introduction 6001 2 Ultrasonic waves in condensed matter 6002 2.1 Crystalline elasticity 6002 2.2 Plane-wave propagation methods 6003 3 Resonant ultrasound spectroscopy 6005 4 Theoretical basis of RUS 6008 4.1 Computation of the eigenfrequencies 6008 4.1.1 The general computational method. 6009 4.1.2 Use of symmetry to speed the calculations. 6011 4.2 Determination of the sample parameters 6017 4.2.1 Minimization of the error function. 6017 4.2.2 Calculation of the derivatives of the error function. 6017 4.3 Effects of dissipation 6019 5 Applications of RUS 6020 5.1 Phase transitions 6020 5.2 Hydrogen-metal systems 6024 5.3 Other uses 6025 5.4 Outlook 6025 6 Conclusions 6027

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“…The phenomenon is mainly observed in metals, for example, it was initially observed in the context of aluminum 26 . In metals, the dominant mechanism of coupling is time varying electric field gradient generated by ultrasonic wave and dynamic dipolar interaction, where acoustic waves induce microscopic currents and time varying radio frequency magnetic fields, which interact with magnetic dipole moments 27 . The magnetic spin of nuclei, polarized under an external static field, can absorb acoustic waves under spin-lattice interaction.…”

Section: Introductionmentioning

confidence: 99%

Generation of acoustic-Brownian noise in nuclear magnetic resonance under non-equilibrium thermal fluctuations

Sinha

2020

Sci Rep

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We present an analytical study on generation of acoustic-Brownian noise in nuclear magnetic resonance (NMR) induced as a result of thermal fluctuations of the magnetic moments under non-equilibrium thermal interactions which has not been explored independent of Nyquist–Johnson noise until now. The mechanism of physical coupling between non-equilibrium thermal fluctuations and magnetic moments is illustrated using Lighthill’s formulation on suspension dynamics. We discover that unlike Nyquist–Johnson noise which has a uniform spectral density across a range of frequencies, the spectral dependence of acoustic-Brownian noise decreases with an increase in frequency and resembles Brownian noise associated with a particle in a potential well. The results have applications in the field of image enhancement algorithm as well as noise reduction instrumentation in NMR systems.

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Nuclear-Acoustic-Resonance Absorption and Dispersion in Aluminum

Cited by 17 publications

References 14 publications

On the Limits of Indetermination and on the Set of Limit Functions of Series in the Walsh System

On the Limits of Indetermination and on the Set of Limit Functions of Series in the Walsh System

Resonant ultrasound spectroscopy

Generation of acoustic-Brownian noise in nuclear magnetic resonance under non-equilibrium thermal fluctuations

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