Alpher-Rubin Ultrasonic Attenuation and Dipolar Nuclear-Acoustic-Resonance Coupling in Pure Metals

Experimental results are presented of measurements of the very small magnetic-field-dependent changes in the attenuation $\Delta \alpha$ of ultrasound (absorptive Alpher-Rubin effect) in pure single crystals of Al, Cu, Nb, and Ta. Measurements were made at 293 K in magnetic fields ranging from 0 to 11 kOe, using both longitudinal and transverse acoustic waves. Variations of $\Delta \alpha$ with both orientation and magnitude of the external magnetic field were studied. Measurements of the dependence of $\Delta \alpha$ on frequency over the range 5-250 MHz were made. The results are particularly relevant to the study of induced dipolar coupling in nuclear acoustic resonance. A derivation is given of expressions for the nuclear-acoustic-resonance signal in pure metals.