Acoustic measurements on single crystals of HoVO
4
at a frequency of 800 MHz (Bleaney
et al., Proc. R. Soc. Lond
. A 388, 479 (1983
a
)) revealed the presence of both non-resonant acoustic absorption at low appliedfield strengths and resonant absorption at the enhanced nuclear magnetic resonance frequency. In a recent paper (Bleaney & Gregg
Proc. R. Soc. Lond
. A 413, 313 (1987)) the theory of such acoustic resonance in enhanced nuclear paramagnets has been extended to include other acoustic modes for ions at sites of tetragonal symmetry. In this paper the advantages of using acoustic waves rather than conventional nuclear magnetic resonance for the region 1-2 GHz is described, together with the preparation of transducers of ZnO and the experimental apparatus. Measurements of the acoustic velocities at 1 GHz in HoVO
4
are compared with those of (Goto
et al., J. Phys. Soc. Japan
55, 1613 (1986)) at 10 MHz. Further measurements of the non-resonant and resonant attenuation will be presented in papers III and IV (Bleaney
et al., Proc. R. Soc. Lond
. A 416, 83; 93 (1988)), together with the appropriate theory.
Measuring the spin polarization of alkali-metal atoms using nuclear magnetic resonance frequency shifts of noble gases
