Nuclear acoustical resonance in aluminum in the intermediate temperature region

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Abstract
Further investigations of the anomalous nuclear acoustical resonance (NAR) signals in aluminum have revealed that the amplitude and phase of the resonance signal are temperature dependent via the attenuation and phase shift of the low-frequency modulation field in the metal crystal. Analytic solutions of the modulation signal inside a cylindrical sample are given and their comparisons with the NAR results in pure aluminum and a dilute aluminum-zinc alloy are reasonably good. The Hall coefficients of Al and Al-0.14-at.% Zn were measured in high magnetic fields and over a temperature range relevant to the acoustical-resonance experiments. In both metals the resonance signals did not vanish in the temperature-field region where the Hall coefficient reverses sign. Revision of the existing theory on NAR dipolar coupling may be needed to explain the results.