Further studies of the enhanced nuclear magnet HoVO 4 - III. The non-resonant magnetoacoustic absorption

Abstract

In an earlier paper Bleaney et al . ( Proc. R. Soc. Lond . A 389, 479 (1983)) have used acoustic waves at frequencies of order 800 MHz to study the enhanced nuclear resonant absorption of 165 Ho ( I = 7/2) in the tetragonal Van Vleck magnet HoVO 4 . They observed also a large non-resonant absorption, that vanished on the application of a magnetic field or reduction of the temperature to below 2 K. The variation of this non-resonant absorption with frequency, magnetic field and temperature is reported in this paper, and shown to agree with theory. Measurements have been made on single crystals both of HoVO 4 , and of (0.1 Ho, 0.9Y) VO 4 . The generation and detection of such acoustic waves, together with measurements of their velocities, have been described in paper II of this series (Bleaney et al., Proc. R. Soc. Lond . A 416, 75 (1988 a )).